diff --git a/ci/bin/format.dart b/ci/bin/format.dart
index 73e8f6a8f9a6e..093900067fdbb 100644
--- a/ci/bin/format.dart
+++ b/ci/bin/format.dart
@@ -725,7 +725,11 @@ class PythonFormatChecker extends FormatChecker {
   }
 
   Future<int> _runYapfCheck({required bool fixing}) async {
-    final List<String> filesToCheck = await getFileList(<String>['*.py']);
+    final List<String> filesToCheck = <String>[
+      ...await getFileList(<String>['*.py']),
+      // Always include flutter/tools/gn.
+      '${repoDir.path}/tools/gn',
+    ];
 
     final List<String> cmd = <String>[
       yapfBin.path,
diff --git a/tools/gn b/tools/gn
index 1ded9d53aeb69..0c0d078a843d9 100755
--- a/tools/gn
+++ b/tools/gn
@@ -13,87 +13,97 @@ import sys
 import os
 import platform
 
-SRC_ROOT = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+SRC_ROOT = os.path.dirname(
+    os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+)
+
 
 def get_out_dir(args):
-    if args.target_os is not None:
-        target_dir = [args.target_os]
-    else:
-        target_dir = ['host']
+  if args.target_os is not None:
+    target_dir = [args.target_os]
+  else:
+    target_dir = ['host']
 
-    runtime_mode = args.runtime_mode
+  runtime_mode = args.runtime_mode
 
-    target_dir.append(args.runtime_mode)
+  target_dir.append(args.runtime_mode)
 
-    if args.simulator:
-        target_dir.append('sim')
+  if args.simulator:
+    target_dir.append('sim')
 
-    if args.unoptimized:
-        target_dir.append('unopt')
+  if args.unoptimized:
+    target_dir.append('unopt')
 
-    if args.target_os != 'ios' and args.interpreter:
-        target_dir.append('interpreter')
+  if args.target_os != 'ios' and args.interpreter:
+    target_dir.append('interpreter')
 
-    if args.android_cpu != 'arm':
-        target_dir.append(args.android_cpu)
+  if args.android_cpu != 'arm':
+    target_dir.append(args.android_cpu)
 
-    if args.ios_cpu != 'arm64':
-        target_dir.append(args.ios_cpu)
+  if args.ios_cpu != 'arm64':
+    target_dir.append(args.ios_cpu)
 
-    if args.mac_cpu != 'x64':
-      target_dir.append(args.mac_cpu)
+  if args.mac_cpu != 'x64':
+    target_dir.append(args.mac_cpu)
 
-    if args.simulator_cpu != 'x64':
-        target_dir.append(args.simulator_cpu)
+  if args.simulator_cpu != 'x64':
+    target_dir.append(args.simulator_cpu)
 
-    if args.linux_cpu is not None:
-      target_dir.append(args.linux_cpu)
+  if args.linux_cpu is not None:
+    target_dir.append(args.linux_cpu)
 
-    if args.windows_cpu != 'x64':
-      target_dir.append(args.windows_cpu)
+  if args.windows_cpu != 'x64':
+    target_dir.append(args.windows_cpu)
 
-    if args.target_os == 'fuchsia' and args.fuchsia_cpu is not None:
-      target_dir.append(args.fuchsia_cpu)
+  if args.target_os == 'fuchsia' and args.fuchsia_cpu is not None:
+    target_dir.append(args.fuchsia_cpu)
 
-    if args.support_fractional_translation:
-      target_dir.append('fractional')
+  if args.support_fractional_translation:
+    target_dir.append('fractional')
 
-    # This exists for backwards compatibility of tests that are being run
-    # on LUCI. This can be removed in coordination with a LUCI change:
-    # https://github.com/flutter/flutter/issues/76547
-    if args.macos_enable_metal:
-      target_dir.append('metal')
+  # This exists for backwards compatibility of tests that are being run
+  # on LUCI. This can be removed in coordination with a LUCI change:
+  # https://github.com/flutter/flutter/issues/76547
+  if args.macos_enable_metal:
+    target_dir.append('metal')
 
-    if args.target_dir != '':
-      target_dir = [args.target_dir]
+  if args.target_dir != '':
+    target_dir = [args.target_dir]
+
+  return os.path.join(args.out_dir, 'out', '_'.join(target_dir))
 
-    return os.path.join(args.out_dir, 'out', '_'.join(target_dir))
 
 def to_command_line(gn_args):
-    """Converts the arguments dictionary to a list of command-line arguments.
+  """Converts the arguments dictionary to a list of command-line arguments.
 
     Args:
       gn_args: GN arguments dictionary generated by to_gn_args().
     """
-    def merge(key, value):
-        if type(value) is bool:
-            return '%s=%s' % (key, 'true' if value else 'false')
-        return '%s="%s"' % (key, value)
-    return [merge(x, y) for x, y in gn_args.items()]
+
+  def merge(key, value):
+    if type(value) is bool:
+      return '%s=%s' % (key, 'true' if value else 'false')
+    return '%s="%s"' % (key, value)
+
+  return [merge(x, y) for x, y in gn_args.items()]
+
 
 def cpu_for_target_arch(arch):
-  if arch in ['ia32', 'x86', 'arm', 'armv6', 'armv5te', 'mips',
-              'simarm', 'simarmv6', 'simarmv5te', 'simmips', 'simdbc',
-              'armsimdbc']:
+  if arch in ['ia32', 'x86', 'arm', 'armv6', 'armv5te', 'mips', 'simarm',
+              'simarmv6', 'simarmv5te', 'simmips', 'simdbc', 'armsimdbc']:
     return 'x86'
   if arch in ['x64', 'arm64', 'simarm64', 'simdbc64', 'armsimdbc64']:
     return 'x64'
 
+
 def is_host_build(args):
-    # If target_os == None, then this is a host build.
-    # However, for linux arm64 builds, we cross compile from x64 hosts, so the
-    # target_os='linux' and linux-cpu='arm64'
-    return args.target_os is None or (args.target_os == 'linux' and args.linux_cpu == 'arm64')
+  # If target_os == None, then this is a host build.
+  # However, for linux arm64 builds, we cross compile from x64 hosts, so the
+  # target_os='linux' and linux-cpu='arm64'
+  return args.target_os is None or (
+      args.target_os == 'linux' and args.linux_cpu == 'arm64'
+  )
+
 
 # Determines whether a prebuilt Dart SDK can be used instead of building one.
 # We can use a prebuilt Dart SDK when:
@@ -192,318 +202,341 @@ def get_target_cpu(args):
 
 
 def to_gn_args(args):
-    if args.simulator:
-        if args.target_os != 'ios':
-            raise Exception('--simulator is only supported for iOS')
-
-    runtime_mode = args.runtime_mode
-
-    gn_args = {}
-
-    if args.bitcode:
-      if args.target_os != 'ios':
-        raise Exception('Bitcode is only supported for iOS')
-      if runtime_mode != 'release':
-        gn_args['bitcode_marker'] = True
-
-    gn_args['enable_bitcode'] = args.bitcode
-    if args.enable_unittests:
-        gn_args['enable_unittests'] = args.enable_unittests
-
-    # Skia GN args.
-    gn_args['skia_enable_flutter_defines'] = True # Enable Flutter API guards in Skia.
-    gn_args['skia_use_dng_sdk'] = False    # RAW image handling.
-    gn_args['skia_use_sfntly'] = False     # PDF handling dependency.
-    gn_args['skia_enable_pdf'] = False     # PDF handling.
-    gn_args['skia_use_x11'] = False        # Never add the X11 dependency (only takes effect on Linux).
-    gn_args['skia_use_wuffs'] = True
-    gn_args['skia_use_expat'] = args.target_os == 'android'
-    gn_args['skia_use_fontconfig'] = args.enable_fontconfig
-
-    if args.enable_skshaper:
-      gn_args['skia_use_icu'] = True
-      if args.target_os != 'wasm':
-        gn_args['flutter_always_use_skshaper'] = args.always_use_skshaper
-      else:
-        gn_args['skia_use_harfbuzz'] = True
-        gn_args['icu_use_data_file'] = False
-    gn_args['is_official_build'] = True    # Disable Skia test utilities.
-    gn_args['is_debug'] = args.unoptimized
-    gn_args['android_full_debug'] = args.target_os == 'android' and args.unoptimized
-    if args.clang is None:
-      gn_args['is_clang'] = True
+  if args.simulator:
+    if args.target_os != 'ios':
+      raise Exception('--simulator is only supported for iOS')
+
+  runtime_mode = args.runtime_mode
+
+  gn_args = {}
+
+  if args.bitcode:
+    if args.target_os != 'ios':
+      raise Exception('Bitcode is only supported for iOS')
+    if runtime_mode != 'release':
+      gn_args['bitcode_marker'] = True
+
+  gn_args['enable_bitcode'] = args.bitcode
+  if args.enable_unittests:
+    gn_args['enable_unittests'] = args.enable_unittests
+
+  # Skia GN args.
+  gn_args['skia_enable_flutter_defines'
+         ] = True  # Enable Flutter API guards in Skia.
+  gn_args['skia_use_dng_sdk'] = False  # RAW image handling.
+  gn_args['skia_use_sfntly'] = False  # PDF handling dependency.
+  gn_args['skia_enable_pdf'] = False  # PDF handling.
+  gn_args['skia_use_x11'
+         ] = False  # Never add the X11 dependency (only takes effect on Linux).
+  gn_args['skia_use_wuffs'] = True
+  gn_args['skia_use_expat'] = args.target_os == 'android'
+  gn_args['skia_use_fontconfig'] = args.enable_fontconfig
+
+  if args.enable_skshaper:
+    gn_args['skia_use_icu'] = True
+    if args.target_os != 'wasm':
+      gn_args['flutter_always_use_skshaper'] = args.always_use_skshaper
     else:
-      gn_args['is_clang'] = args.clang
-
-    if args.target_os == 'android' or args.target_os == 'ios':
-      gn_args['skia_gl_standard'] = 'gles'
-    elif args.target_os == 'wasm':
-      gn_args['skia_gl_standard'] = 'webgl'
+      gn_args['skia_use_harfbuzz'] = True
+      gn_args['icu_use_data_file'] = False
+  gn_args['is_official_build'] = True  # Disable Skia test utilities.
+  gn_args['is_debug'] = args.unoptimized
+  gn_args['android_full_debug'
+         ] = args.target_os == 'android' and args.unoptimized
+  if args.clang is None:
+    gn_args['is_clang'] = True
+  else:
+    gn_args['is_clang'] = args.clang
+
+  if args.target_os == 'android' or args.target_os == 'ios':
+    gn_args['skia_gl_standard'] = 'gles'
+  elif args.target_os == 'wasm':
+    gn_args['skia_gl_standard'] = 'webgl'
+  else:
+    # We explicitly don't want to pick GL because we run GLES tests using SwiftShader.
+    gn_args['skia_gl_standard'] = ''
+
+  if not sys.platform.startswith(('cygwin', 'win')):
+    gn_args['use_clang_static_analyzer'] = args.clang_static_analyzer
+
+  gn_args['enable_coverage'] = args.coverage
+
+  if args.operator_new_alignment is not None:
+    gn_args['operator_new_alignment'] = args.operator_new_alignment
+
+  enable_lto = args.lto
+  if args.unoptimized:
+    # There is no point in enabling LTO in unoptimized builds.
+    enable_lto = False
+
+  if not sys.platform.startswith('win'):
+    # The GN arg is not available in the windows toolchain.
+    gn_args['enable_lto'] = enable_lto
+
+  # Set OS, CPU arch for host or target build.
+  if is_host_build(args):
+    gn_args['host_os'] = get_host_os()
+    gn_args['host_cpu'] = get_host_cpu(args)
+    gn_args['target_os'] = gn_args['host_os']
+    gn_args['target_cpu'] = get_target_cpu(args)
+    gn_args['dart_target_arch'] = gn_args['target_cpu']
+  else:
+    gn_args['target_os'] = args.target_os
+    gn_args['target_cpu'] = get_target_cpu(args)
+    gn_args['dart_target_arch'] = gn_args['target_cpu']
+
+  # No cross-compilation on Windows (for now). Use host toolchain that
+  # matches the bit-width of the target architecture.
+  if sys.platform.startswith(('cygwin', 'win')) and args.target_os != 'win':
+    gn_args['host_cpu'] = cpu_for_target_arch(gn_args['target_cpu'])
+    gn_args['target_cpu'] = cpu_for_target_arch(gn_args['target_cpu'])
+
+  # macOS host builds (whether x64 or arm64) must currently be built under
+  # Rosetta on Apple Silicon Macs.
+  # TODO(cbracken): https://github.com/flutter/flutter/issues/103386
+  if is_host_build(args) and gn_args['host_os'] == 'mac':
+    gn_args['host_cpu'] = 'x64'
+
+  # macOS target builds (whether x64 or arm64) must currently be built under
+  # Rosetta on Apple Silicon Macs.
+  # TODO(cbracken): https://github.com/flutter/flutter/issues/103386
+  if 'target_os' in gn_args and gn_args['target_os'] == 'mac':
+    gn_args['host_cpu'] = 'x64'
+
+  if gn_args['target_os'] == 'ios':
+    gn_args['use_ios_simulator'] = args.simulator
+  else:
+    gn_args['use_ios_simulator'] = False
+
+  if args.dart_debug:
+    gn_args['dart_debug'] = True
+
+  if args.full_dart_debug:
+    gn_args['dart_debug'] = True
+    gn_args['dart_debug_optimization_level'] = '0'
+
+  # Flutter-specific arguments which don't apply for a CanvasKit build.
+  if args.target_os != 'wasm':
+    gn_args['flutter_use_fontconfig'] = args.enable_fontconfig
+    gn_args['flutter_enable_skshaper'] = args.enable_skshaper
+    gn_args['dart_component_kind'
+           ] = 'static_library'  # Always link Dart in statically.
+    gn_args['embedder_for_target'] = args.embedder_for_target
+    gn_args['dart_lib_export_symbols'] = False
+    gn_args['flutter_runtime_mode'] = runtime_mode
+    gn_args['full_dart_sdk'] = args.full_dart_sdk
+    gn_args['dart_version_git_info'] = not args.no_dart_version_git_info
+
+    gn_args['dart_lib_export_symbols'] = False
+    if runtime_mode == 'debug':
+      gn_args['dart_runtime_mode'] = 'develop'
+    elif runtime_mode == 'jit_release':
+      gn_args['dart_runtime_mode'] = 'release'
     else:
-      # We explicitly don't want to pick GL because we run GLES tests using SwiftShader.
-      gn_args['skia_gl_standard'] = ''
-
-    if not sys.platform.startswith(('cygwin', 'win')):
-      gn_args['use_clang_static_analyzer'] = args.clang_static_analyzer
-
-    gn_args['enable_coverage'] = args.coverage
+      gn_args['dart_runtime_mode'] = runtime_mode
 
-    if args.operator_new_alignment is not None:
-      gn_args['operator_new_alignment'] = args.operator_new_alignment
+    # Desktop embeddings can have more dependencies than the engine library,
+    # which can be problematic in some build environments (e.g., building on
+    # Linux will bring in pkg-config dependencies at generation time). These
+    # flags allow preventing those those targets from being part of the build
+    # tree.
+    gn_args['enable_desktop_embeddings'] = not args.disable_desktop_embeddings
 
-    enable_lto = args.lto
-    if args.unoptimized:
-      # There is no point in enabling LTO in unoptimized builds.
-      enable_lto = False
+    # Overrides whether Boring SSL is compiled with system as. Only meaningful
+    # on Android.
+    gn_args['bssl_use_clang_integrated_as'] = True
 
-    if not sys.platform.startswith('win'):
-      # The GN arg is not available in the windows toolchain.
-      gn_args['enable_lto'] = enable_lto
-
-    # Set OS, CPU arch for host or target build.
-    if is_host_build(args):
-      gn_args['host_os'] = get_host_os()
-      gn_args['host_cpu'] = get_host_cpu(args)
-      gn_args['target_os'] = gn_args['host_os']
-      gn_args['target_cpu'] = get_target_cpu(args)
-      gn_args['dart_target_arch'] = gn_args['target_cpu']
-    else:
-      gn_args['target_os'] = args.target_os
-      gn_args['target_cpu'] = get_target_cpu(args)
-      gn_args['dart_target_arch'] = gn_args['target_cpu']
-
-    # No cross-compilation on Windows (for now). Use host toolchain that
-    # matches the bit-width of the target architecture.
-    if sys.platform.startswith(('cygwin', 'win')) and args.target_os != 'win':
-      gn_args['host_cpu'] = cpu_for_target_arch(gn_args['target_cpu'])
-      gn_args['target_cpu'] = cpu_for_target_arch(gn_args['target_cpu'])
-
-    # macOS host builds (whether x64 or arm64) must currently be built under
-    # Rosetta on Apple Silicon Macs.
-    # TODO(cbracken): https://github.com/flutter/flutter/issues/103386
-    if is_host_build(args) and gn_args['host_os'] == 'mac':
-      gn_args['host_cpu'] = 'x64'
-
-    # macOS target builds (whether x64 or arm64) must currently be built under
-    # Rosetta on Apple Silicon Macs.
-    # TODO(cbracken): https://github.com/flutter/flutter/issues/103386
-    if 'target_os' in gn_args and gn_args['target_os'] == 'mac':
-      gn_args['host_cpu'] = 'x64'
-
-    if gn_args['target_os'] == 'ios':
-      gn_args['use_ios_simulator'] = args.simulator
-    else:
-      gn_args['use_ios_simulator'] = False
+  if args.allow_deprecated_api_calls:
+    gn_args['allow_deprecated_api_calls'] = args.allow_deprecated_api_calls
 
-    if args.dart_debug:
-        gn_args['dart_debug'] = True
+  if args.support_fractional_translation:
+    gn_args['support_fractional_translation'
+           ] = args.support_fractional_translation
 
-    if args.full_dart_debug:
-      gn_args['dart_debug'] = True
-      gn_args['dart_debug_optimization_level'] = '0'
-
-    # Flutter-specific arguments which don't apply for a CanvasKit build.
-    if args.target_os != 'wasm':
-      gn_args['flutter_use_fontconfig'] = args.enable_fontconfig
-      gn_args['flutter_enable_skshaper'] = args.enable_skshaper
-      gn_args['dart_component_kind'] = 'static_library' # Always link Dart in statically.
-      gn_args['embedder_for_target'] = args.embedder_for_target
-      gn_args['dart_lib_export_symbols'] = False
-      gn_args['flutter_runtime_mode'] = runtime_mode
-      gn_args['full_dart_sdk'] = args.full_dart_sdk
-      gn_args['dart_version_git_info'] = not args.no_dart_version_git_info
-
-      gn_args['dart_lib_export_symbols'] = False
-      if runtime_mode == 'debug':
-          gn_args['dart_runtime_mode'] = 'develop'
-      elif runtime_mode == 'jit_release':
-          gn_args['dart_runtime_mode'] = 'release'
-      else:
-          gn_args['dart_runtime_mode'] = runtime_mode
-
-      # Desktop embeddings can have more dependencies than the engine library,
-      # which can be problematic in some build environments (e.g., building on
-      # Linux will bring in pkg-config dependencies at generation time). These
-      # flags allow preventing those those targets from being part of the build
-      # tree.
-      gn_args['enable_desktop_embeddings'] = not args.disable_desktop_embeddings
-
-      # Overrides whether Boring SSL is compiled with system as. Only meaningful
-      # on Android.
-      gn_args['bssl_use_clang_integrated_as'] = True
-
-    if args.allow_deprecated_api_calls:
-      gn_args['allow_deprecated_api_calls'] = args.allow_deprecated_api_calls
-
-    if args.support_fractional_translation:
-      gn_args['support_fractional_translation'] = args.support_fractional_translation
-
-    # DBC is not supported anymore.
-    if args.interpreter:
-      raise Exception('--interpreter is no longer needed on any supported platform.')
-
-    if args.target_os is None:
-      if sys.platform.startswith(('cygwin', 'win')):
-        gn_args['dart_use_fallback_root_certificates'] = True
-
-    if args.target_sysroot:
-      gn_args['target_sysroot'] = args.target_sysroot
-      gn_args['custom_sysroot'] = args.target_sysroot
-
-    if args.target_toolchain:
-      gn_args['custom_toolchain'] = args.target_toolchain
-
-    if args.target_triple:
-      gn_args['custom_target_triple'] = args.target_triple
-
-    goma_dir = os.environ.get('GOMA_DIR')
-    goma_home_dir = os.path.join(os.getenv('HOME', ''), 'goma')
-    depot_tools_bin_dir = os.path.join(args.depot_tools, '.cipd_bin')
-
-    # GOMA has a different default (home) path on gWindows.
-    if not os.path.exists(goma_home_dir) and sys.platform.startswith(('cygwin', 'win')):
-      goma_home_dir = os.path.join('c:\\', 'src', 'goma', 'goma-win64')
-
-    if args.goma and goma_dir:
-      gn_args['use_goma'] = True
-      gn_args['goma_dir'] = goma_dir
-    elif args.goma and os.path.exists(goma_home_dir):
-      gn_args['use_goma'] = True
-      gn_args['goma_dir'] = goma_home_dir
-    elif args.goma and os.path.exists(depot_tools_bin_dir):
-      gn_args['use_goma'] = True
-      gn_args['goma_dir'] = depot_tools_bin_dir
-    else:
-      if args.goma:
-        print("GOMA usage was specified but can't be found, falling back to local builds. Set the GOMA_DIR environment variable to fix GOMA.")
-      gn_args['use_goma'] = False
-      gn_args['goma_dir'] = None
-
-    if gn_args['use_goma']:
-      if args.xcode_symlinks or os.getenv('FLUTTER_GOMA_CREATE_XCODE_SYMLINKS', '0') == '1':
-        gn_args['create_xcode_symlinks'] = True
-
-    # Enable Metal on iOS builds.
-    if args.target_os == 'ios':
-      gn_args['skia_use_metal'] = True
-      gn_args['shell_enable_metal'] = True
-      # Bitcode enabled builds using the current version of the toolchain leak
-      # C++ symbols decorated with the availability attribute. Disable these
-      # attributes in release modes till the toolchain is updated.
-      gn_args['skia_enable_api_available_macro'] = args.runtime_mode != "release"
-
-    if sys.platform == 'darwin' and args.target_os not in ['android', 'fuchsia', 'wasm']:
-      # OpenGL is deprecated on macOS > 10.11.
-      # This is not necessarily needed but enabling this until we have a way to
-      # build a macOS metal only shell and a gl only shell.
-      gn_args['allow_deprecated_api_calls'] = True
-      gn_args['skia_use_metal'] = True
-      gn_args['shell_enable_metal'] = True
-
-    # Enable Vulkan on all platforms except for Android and iOS. This is just
-    # to save on mobile binary size, as there's no reason the Vulkan embedder
-    # features can't work on these platforms.
-    if args.target_os not in ['android', 'ios', 'wasm']:
-      gn_args['skia_use_vulkan'] = True
-      gn_args['shell_enable_vulkan'] = True
-      # Disable VMA's use of std::shared_mutex in environments where the
-      # standard library doesn't support it.
-      if args.target_os == 'ios' or sys.platform.startswith(('cygwin', 'win')):
-        gn_args['skia_disable_vma_stl_shared_mutex'] = True
+  # DBC is not supported anymore.
+  if args.interpreter:
+    raise Exception(
+        '--interpreter is no longer needed on any supported platform.'
+    )
 
+  if args.target_os is None:
     if sys.platform.startswith(('cygwin', 'win')):
-      # The buildroot currently isn't set up to support Vulkan in the
-      # Windows ANGLE build, so disable it regardless of enable_vulkan's value.
-      gn_args['angle_enable_vulkan'] = False
-      # Don't build unnecessary portions of the ANGLE tree.
-      gn_args['angle_build_all'] = False
-
-    # We should not need a special case for x86, but this seems to introduce text relocations
-    # even with -fPIC everywhere.
-    # gn_args['enable_profiling'] = args.runtime_mode != 'release' and args.android_cpu != 'x86'
-
-    # Make symbols visible in order to enable symbolization of unit test crash backtraces on Linux
-    gn_args['disable_hidden_visibility'] = args.target_os == 'linux' and args.unoptimized
-
-    if args.arm_float_abi:
-      gn_args['arm_float_abi'] = args.arm_float_abi
-
-    # If we have a prebuilt for the Dart SDK for the target architecture, then
-    # use it instead of building a new one.
-    if args.prebuilt_dart_sdk:
-      if can_use_prebuilt_dart(args):
-        print('Using prebuilt Dart SDK binary. If you are editing Dart sources '
-              'and wish to compile the Dart SDK, set `--no-prebuilt-dart-sdk`.')
-        gn_args['flutter_prebuilt_dart_sdk'] = True
-        gn_args['dart_sdk_output'] = 'built-dart-sdk'
-      elif is_host_build(args):
-        print('Tried to download prebuilt Dart SDK but an appropriate version '
-                'could not be found!')
-        print('Either retry by running '
-              'flutter/tools/download_dart_sdk.py manually or compile from '
-              'source by setting `--no-prebuilt-dart-sdk` flag to tools/gn')
-    elif is_host_build(args):
-      # dart_platform_sdk is only defined for host builds, linux arm host builds
-      # specify target_os=linux.
-      # dart_platform_sdk=True means exclude web-related files, e.g. dart2js,
-      # dartdevc, web SDK kernel and source files.
-      gn_args['dart_platform_sdk'] = not args.full_dart_sdk
-
-    if args.build_glfw_shell is not None:
-      gn_args['build_glfw_shell'] = args.build_glfw_shell
-
-    if args.build_embedder_examples is not None:
-      gn_args['build_embedder_examples'] = args.build_embedder_examples
-
-    gn_args['stripped_symbols'] = args.stripped
-
-    if args.msan:
-      gn_args['is_msan'] = True
-
-    if args.asan:
-      gn_args['is_asan'] = True
-
-    if args.tsan:
-      gn_args['is_tsan'] = True
-
-    if args.lsan:
-      gn_args['is_lsan'] = True
-
-    if args.ubsan:
-      gn_args['is_ubsan'] = True
-
-    if args.enable_vulkan_validation_layers:
-      if args.target_os != 'fuchsia':
-        print('Vulkan validation layers are currently only supported on Fuchsia targets.')
-        sys.exit(1)
-      gn_args['enable_vulkan_validation_layers'] = True
-
-
-    # Enable pointer compression on 64-bit mobile targets.
-    if args.target_os in ['android', 'ios'] and gn_args['target_cpu'] in ['x64' , 'arm64']:
-      gn_args['dart_use_compressed_pointers'] = True
+      gn_args['dart_use_fallback_root_certificates'] = True
+
+  if args.target_sysroot:
+    gn_args['target_sysroot'] = args.target_sysroot
+    gn_args['custom_sysroot'] = args.target_sysroot
+
+  if args.target_toolchain:
+    gn_args['custom_toolchain'] = args.target_toolchain
+
+  if args.target_triple:
+    gn_args['custom_target_triple'] = args.target_triple
+
+  goma_dir = os.environ.get('GOMA_DIR')
+  goma_home_dir = os.path.join(os.getenv('HOME', ''), 'goma')
+  depot_tools_bin_dir = os.path.join(args.depot_tools, '.cipd_bin')
+
+  # GOMA has a different default (home) path on gWindows.
+  if not os.path.exists(goma_home_dir) and sys.platform.startswith(
+      ('cygwin', 'win')):
+    goma_home_dir = os.path.join('c:\\', 'src', 'goma', 'goma-win64')
+
+  if args.goma and goma_dir:
+    gn_args['use_goma'] = True
+    gn_args['goma_dir'] = goma_dir
+  elif args.goma and os.path.exists(goma_home_dir):
+    gn_args['use_goma'] = True
+    gn_args['goma_dir'] = goma_home_dir
+  elif args.goma and os.path.exists(depot_tools_bin_dir):
+    gn_args['use_goma'] = True
+    gn_args['goma_dir'] = depot_tools_bin_dir
+  else:
+    if args.goma:
+      print(
+          "GOMA usage was specified but can't be found, falling back to local builds. Set the GOMA_DIR environment variable to fix GOMA."
+      )
+    gn_args['use_goma'] = False
+    gn_args['goma_dir'] = None
+
+  if gn_args['use_goma']:
+    if args.xcode_symlinks or os.getenv('FLUTTER_GOMA_CREATE_XCODE_SYMLINKS',
+                                        '0') == '1':
+      gn_args['create_xcode_symlinks'] = True
+
+  # Enable Metal on iOS builds.
+  if args.target_os == 'ios':
+    gn_args['skia_use_metal'] = True
+    gn_args['shell_enable_metal'] = True
+    # Bitcode enabled builds using the current version of the toolchain leak
+    # C++ symbols decorated with the availability attribute. Disable these
+    # attributes in release modes till the toolchain is updated.
+    gn_args['skia_enable_api_available_macro'] = args.runtime_mode != "release"
+
+  if sys.platform == 'darwin' and args.target_os not in ['android', 'fuchsia',
+                                                         'wasm']:
+    # OpenGL is deprecated on macOS > 10.11.
+    # This is not necessarily needed but enabling this until we have a way to
+    # build a macOS metal only shell and a gl only shell.
+    gn_args['allow_deprecated_api_calls'] = True
+    gn_args['skia_use_metal'] = True
+    gn_args['shell_enable_metal'] = True
+
+  # Enable Vulkan on all platforms except for Android and iOS. This is just
+  # to save on mobile binary size, as there's no reason the Vulkan embedder
+  # features can't work on these platforms.
+  if args.target_os not in ['android', 'ios', 'wasm']:
+    gn_args['skia_use_vulkan'] = True
+    gn_args['shell_enable_vulkan'] = True
+    # Disable VMA's use of std::shared_mutex in environments where the
+    # standard library doesn't support it.
+    if args.target_os == 'ios' or sys.platform.startswith(('cygwin', 'win')):
+      gn_args['skia_disable_vma_stl_shared_mutex'] = True
 
-    if args.fuchsia_target_api_level is not None:
-      gn_args['fuchsia_target_api_level'] = args.fuchsia_target_api_level
-    elif args.target_os == 'fuchsia':
-      # Read the default target api level from a file so we can update it with a roller
-      with open(os.path.join(os.path.dirname(__file__), 'fuchsia/target_api_level')) as f:
-        gn_args['fuchsia_target_api_level'] = int(f.read().strip())
+  if sys.platform.startswith(('cygwin', 'win')):
+    # The buildroot currently isn't set up to support Vulkan in the
+    # Windows ANGLE build, so disable it regardless of enable_vulkan's value.
+    gn_args['angle_enable_vulkan'] = False
+    # Don't build unnecessary portions of the ANGLE tree.
+    gn_args['angle_build_all'] = False
+
+  # We should not need a special case for x86, but this seems to introduce text relocations
+  # even with -fPIC everywhere.
+  # gn_args['enable_profiling'] = args.runtime_mode != 'release' and args.android_cpu != 'x86'
+
+  # Make symbols visible in order to enable symbolization of unit test crash backtraces on Linux
+  gn_args['disable_hidden_visibility'
+         ] = args.target_os == 'linux' and args.unoptimized
+
+  if args.arm_float_abi:
+    gn_args['arm_float_abi'] = args.arm_float_abi
+
+  # If we have a prebuilt for the Dart SDK for the target architecture, then
+  # use it instead of building a new one.
+  if args.prebuilt_dart_sdk:
+    if can_use_prebuilt_dart(args):
+      print(
+          'Using prebuilt Dart SDK binary. If you are editing Dart sources '
+          'and wish to compile the Dart SDK, set `--no-prebuilt-dart-sdk`.'
+      )
+      gn_args['flutter_prebuilt_dart_sdk'] = True
+      gn_args['dart_sdk_output'] = 'built-dart-sdk'
+    elif is_host_build(args):
+      print(
+          'Tried to download prebuilt Dart SDK but an appropriate version '
+          'could not be found!'
+      )
+      print(
+          'Either retry by running '
+          'flutter/tools/download_dart_sdk.py manually or compile from '
+          'source by setting `--no-prebuilt-dart-sdk` flag to tools/gn'
+      )
+  elif is_host_build(args):
+    # dart_platform_sdk is only defined for host builds, linux arm host builds
+    # specify target_os=linux.
+    # dart_platform_sdk=True means exclude web-related files, e.g. dart2js,
+    # dartdevc, web SDK kernel and source files.
+    gn_args['dart_platform_sdk'] = not args.full_dart_sdk
+
+  if args.build_glfw_shell is not None:
+    gn_args['build_glfw_shell'] = args.build_glfw_shell
+
+  if args.build_embedder_examples is not None:
+    gn_args['build_embedder_examples'] = args.build_embedder_examples
+
+  gn_args['stripped_symbols'] = args.stripped
+
+  if args.msan:
+    gn_args['is_msan'] = True
+
+  if args.asan:
+    gn_args['is_asan'] = True
+
+  if args.tsan:
+    gn_args['is_tsan'] = True
+
+  if args.lsan:
+    gn_args['is_lsan'] = True
+
+  if args.ubsan:
+    gn_args['is_ubsan'] = True
+
+  if args.enable_vulkan_validation_layers:
+    if args.target_os != 'fuchsia':
+      print(
+          'Vulkan validation layers are currently only supported on Fuchsia targets.'
+      )
+      sys.exit(1)
+    gn_args['enable_vulkan_validation_layers'] = True
+
+  # Enable pointer compression on 64-bit mobile targets.
+  if args.target_os in ['android', 'ios'
+                       ] and gn_args['target_cpu'] in ['x64', 'arm64']:
+    gn_args['dart_use_compressed_pointers'] = True
+
+  if args.fuchsia_target_api_level is not None:
+    gn_args['fuchsia_target_api_level'] = args.fuchsia_target_api_level
+  elif args.target_os == 'fuchsia':
+    # Read the default target api level from a file so we can update it with a roller
+    with open(os.path.join(os.path.dirname(__file__),
+                           'fuchsia/target_api_level')) as f:
+      gn_args['fuchsia_target_api_level'] = int(f.read().strip())
+
+  # Flags for Dart features:
+  if args.use_mallinfo2:
+    gn_args['dart_use_mallinfo2'] = args.use_mallinfo2
 
-    # Flags for Dart features:
-    if args.use_mallinfo2:
-      gn_args['dart_use_mallinfo2'] = args.use_mallinfo2
+  # Impeller flags.
+  if args.enable_impeller_playground:
+    gn_args['impeller_enable_playground'] = args.enable_impeller_playground
+  elif os.getenv('FLUTTER_IMPELLER_ENABLE_PLAYGROUND', '0') == '1':
+    gn_args['impeller_enable_playground'] = True
 
-    # Impeller flags.
-    if args.enable_impeller_playground:
-      gn_args['impeller_enable_playground'] = args.enable_impeller_playground
-    elif os.getenv('FLUTTER_IMPELLER_ENABLE_PLAYGROUND', '0') == '1':
-      gn_args['impeller_enable_playground'] = True
+  if args.prebuilt_impellerc is not None:
+    gn_args['impeller_use_prebuilt_impellerc'] = args.prebuilt_impellerc
 
-    if args.prebuilt_impellerc is not None:
-      gn_args['impeller_use_prebuilt_impellerc'] = args.prebuilt_impellerc
+  return gn_args
 
-    return gn_args
 
 def parse_args(args):
   args = args[1:]
@@ -513,128 +546,304 @@ def parse_args(args):
 
   parser.add_argument('--enable-unittests', action='store_true', default=False)
 
-  parser.add_argument('--runtime-mode', type=str, choices=['debug', 'profile', 'release', 'jit_release'], default='debug')
+  parser.add_argument(
+      '--runtime-mode',
+      type=str,
+      choices=['debug', 'profile', 'release', 'jit_release'],
+      default='debug'
+  )
   parser.add_argument('--interpreter', default=False, action='store_true')
-  parser.add_argument('--dart-debug', default=False, action='store_true', help='Enables assertions in the Dart VM. ' +
-      'Does not affect optimization levels. If you need to disable optimizations in Dart, use --full-dart-debug')
-  parser.add_argument('--no-dart-version-git-info', default=False, action='store_true',
-                      help='Set by default; if unset, turns off the dart SDK git hash check')
-  parser.add_argument('--full-dart-debug', default=False, action='store_true', help='Implies --dart-debug ' +
-      'and also disables optimizations in the Dart VM making it easier to step through VM code in the debugger.')
-
-  parser.add_argument('--target-os', type=str, choices=['android', 'ios', 'mac', 'linux', 'fuchsia', 'wasm', 'win'])
-  parser.add_argument('--android', dest='target_os', action='store_const', const='android')
-  parser.add_argument('--android-cpu', type=str, choices=['arm', 'x64', 'x86', 'arm64'], default='arm')
-  parser.add_argument('--ios', dest='target_os', action='store_const', const='ios')
-  parser.add_argument('--ios-cpu', type=str, choices=['arm', 'arm64'], default='arm64')
-  parser.add_argument('--mac', dest='target_os', action='store_const', const='mac')
-  parser.add_argument('--mac-cpu', type=str, choices=['x64', 'arm64'], default='x64')
+  parser.add_argument(
+      '--dart-debug',
+      default=False,
+      action='store_true',
+      help='Enables assertions in the Dart VM. ' +
+      'Does not affect optimization levels. If you need to disable optimizations in Dart, use --full-dart-debug'
+  )
+  parser.add_argument(
+      '--no-dart-version-git-info',
+      default=False,
+      action='store_true',
+      help='Set by default; if unset, turns off the dart SDK git hash check'
+  )
+  parser.add_argument(
+      '--full-dart-debug',
+      default=False,
+      action='store_true',
+      help='Implies --dart-debug ' +
+      'and also disables optimizations in the Dart VM making it easier to step through VM code in the debugger.'
+  )
+
+  parser.add_argument(
+      '--target-os',
+      type=str,
+      choices=['android', 'ios', 'mac', 'linux', 'fuchsia', 'wasm', 'win']
+  )
+  parser.add_argument(
+      '--android', dest='target_os', action='store_const', const='android'
+  )
+  parser.add_argument(
+      '--android-cpu',
+      type=str,
+      choices=['arm', 'x64', 'x86', 'arm64'],
+      default='arm'
+  )
+  parser.add_argument(
+      '--ios', dest='target_os', action='store_const', const='ios'
+  )
+  parser.add_argument(
+      '--ios-cpu', type=str, choices=['arm', 'arm64'], default='arm64'
+  )
+  parser.add_argument(
+      '--mac', dest='target_os', action='store_const', const='mac'
+  )
+  parser.add_argument(
+      '--mac-cpu', type=str, choices=['x64', 'arm64'], default='x64'
+  )
   parser.add_argument('--simulator', action='store_true', default=False)
-  parser.add_argument('--linux', dest='target_os', action='store_const', const='linux')
-  parser.add_argument('--fuchsia', dest='target_os', action='store_const', const='fuchsia')
-  parser.add_argument('--wasm', dest='target_os', action='store_const', const='wasm')
-  parser.add_argument('--windows', dest='target_os', action='store_const', const='win')
-
-  parser.add_argument('--linux-cpu', type=str, choices=['x64', 'x86', 'arm64', 'arm'])
-  parser.add_argument('--fuchsia-cpu', type=str, choices=['x64', 'arm64'], default = 'x64')
-  parser.add_argument('--windows-cpu', type=str, choices=['x64', 'arm64', 'x86'], default = 'x64')
-  parser.add_argument('--simulator-cpu', type=str, choices=['x64', 'arm64'], default = 'x64')
-  parser.add_argument('--arm-float-abi', type=str, choices=['hard', 'soft', 'softfp'])
+  parser.add_argument(
+      '--linux', dest='target_os', action='store_const', const='linux'
+  )
+  parser.add_argument(
+      '--fuchsia', dest='target_os', action='store_const', const='fuchsia'
+  )
+  parser.add_argument(
+      '--wasm', dest='target_os', action='store_const', const='wasm'
+  )
+  parser.add_argument(
+      '--windows', dest='target_os', action='store_const', const='win'
+  )
+
+  parser.add_argument(
+      '--linux-cpu', type=str, choices=['x64', 'x86', 'arm64', 'arm']
+  )
+  parser.add_argument(
+      '--fuchsia-cpu', type=str, choices=['x64', 'arm64'], default='x64'
+  )
+  parser.add_argument(
+      '--windows-cpu', type=str, choices=['x64', 'arm64', 'x86'], default='x64'
+  )
+  parser.add_argument(
+      '--simulator-cpu', type=str, choices=['x64', 'arm64'], default='x64'
+  )
+  parser.add_argument(
+      '--arm-float-abi', type=str, choices=['hard', 'soft', 'softfp']
+  )
 
   parser.add_argument('--goma', default=True, action='store_true')
   parser.add_argument('--no-goma', dest='goma', action='store_false')
-  parser.add_argument('--xcode-symlinks', action='store_true', help='Set to true for builds targeting macOS or iOS ' +
-      'when using goma. If set, symlinks to the Xcode provided sysroot and SDKs will be created in a generated ' +
-      'folder, which will avoid potential backend errors in Fuchsia RBE. Instead of specifying the flag on each invocation ' +
-      'the FLUTTER_GOMA_CREATE_XCODE_SYMLINKS environment variable may be set to 1 to achieve the same effect.')
-  parser.add_argument('--no-xcode-symlinks', dest='xcode_symlinks', default=False, action='store_false')
-  parser.add_argument('--depot-tools', default='~/depot_tools', type=str,
-                      help='Depot tools provides an alternative location for gomacc in ' +
-                      '/path/to/depot_tools/.cipd_bin')
+  parser.add_argument(
+      '--xcode-symlinks',
+      action='store_true',
+      help='Set to true for builds targeting macOS or iOS ' +
+      'when using goma. If set, symlinks to the Xcode provided sysroot and SDKs will be created in a generated '
+      +
+      'folder, which will avoid potential backend errors in Fuchsia RBE. Instead of specifying the flag on each invocation '
+      +
+      'the FLUTTER_GOMA_CREATE_XCODE_SYMLINKS environment variable may be set to 1 to achieve the same effect.'
+  )
+  parser.add_argument(
+      '--no-xcode-symlinks',
+      dest='xcode_symlinks',
+      default=False,
+      action='store_false'
+  )
+  parser.add_argument(
+      '--depot-tools',
+      default='~/depot_tools',
+      type=str,
+      help='Depot tools provides an alternative location for gomacc in ' +
+      '/path/to/depot_tools/.cipd_bin'
+  )
 
   parser.add_argument('--lto', default=True, action='store_true')
   parser.add_argument('--no-lto', dest='lto', action='store_false')
 
   parser.add_argument('--clang', action='store_const', const=True)
-  parser.add_argument('--no-clang', dest='clang', action='store_const', const=False)
-
-  parser.add_argument('--clang-static-analyzer', default=False, action='store_true')
-  parser.add_argument('--no-clang-static-analyzer', dest='clang_static_analyzer', action='store_false')
+  parser.add_argument(
+      '--no-clang', dest='clang', action='store_const', const=False
+  )
+
+  parser.add_argument(
+      '--clang-static-analyzer', default=False, action='store_true'
+  )
+  parser.add_argument(
+      '--no-clang-static-analyzer',
+      dest='clang_static_analyzer',
+      action='store_false'
+  )
 
   parser.add_argument('--target-sysroot', type=str)
   parser.add_argument('--target-toolchain', type=str)
   parser.add_argument('--target-triple', type=str)
-  parser.add_argument('--operator-new-alignment', dest='operator_new_alignment', type=str, default=None)
-
-  parser.add_argument('--macos-enable-metal', action='store_true', default=False)
+  parser.add_argument(
+      '--operator-new-alignment',
+      dest='operator_new_alignment',
+      type=str,
+      default=None
+  )
+
+  parser.add_argument(
+      '--macos-enable-metal', action='store_true', default=False
+  )
   parser.add_argument('--enable-vulkan', action='store_true', default=False)
 
   parser.add_argument('--enable-fontconfig', action='store_true', default=False)
-  parser.add_argument('--enable-vulkan-validation-layers', action='store_true', default=False)
+  parser.add_argument(
+      '--enable-vulkan-validation-layers', action='store_true', default=False
+  )
 
   parser.add_argument('--enable-skshaper', action='store_true', default=True)
-  parser.add_argument('--no-enable-skshaper', dest='enable_skshaper', action='store_false')
-  parser.add_argument('--always-use-skshaper', action='store_true', default=False)
-
-  parser.add_argument('--embedder-for-target', dest='embedder_for_target', action='store_true', default=False)
+  parser.add_argument(
+      '--no-enable-skshaper', dest='enable_skshaper', action='store_false'
+  )
+  parser.add_argument(
+      '--always-use-skshaper', action='store_true', default=False
+  )
+
+  parser.add_argument(
+      '--embedder-for-target',
+      dest='embedder_for_target',
+      action='store_true',
+      default=False
+  )
 
   parser.add_argument('--coverage', default=False, action='store_true')
 
-  parser.add_argument('--out-dir', default='', type=str,
-                      help='Root out directory. Target specific gn files will be generated in ${out-dir}/')
-  parser.add_argument('--target-dir', default='', type=str,
-                      help='Use the specified name for target out directory. By default this tool determines one.')
-
-  parser.add_argument('--full-dart-sdk', default=False, action='store_true',
-                      help='include trained dart2js and dartdevc snapshots. Enable only on steps that create an SDK')
-  parser.add_argument('--no-full-dart-sdk', dest='full_dart_sdk', action='store_false')
-
-  parser.add_argument('--ide', default='', type=str,
-                      help='The IDE files to generate using GN. Use `gn gen help` and look for the --ide flag to' +
-                      ' see supported IDEs. If this flag is not specified, a platform specific default is selected.')
-
-  parser.add_argument('--allow-deprecated-api-calls', action='store_true', default=False,
-                      help='Turns off warnings about the usage of deprecated APIs.')
-
-  parser.add_argument('--disable-desktop-embeddings', default=False, action='store_true',
-                      help='Do not include desktop embeddings in the build.')
-  parser.add_argument('--build-glfw-shell', action='store_const', const=True,
-                      help='Build the GLFW shell on supported platforms where it is not built by default.')
-  parser.add_argument('--no-build-glfw-shell', dest='build_glfw_shell', action='store_const', const=False,
-                      help='Do not build the GLFW shell on platforms where it is built by default.')
-  parser.add_argument('--build-embedder-examples', action='store_const', const=True,
-                      help='Build the example embedders using the Embedder API.')
-  parser.add_argument('--no-build-embedder-examples', dest='build_embedder_examples', action='store_const', const=False,
-                      help='Do not build the example embedders using the Embedder API.')
-
-  parser.add_argument('--bitcode', default=False, action='store_true',
-                      help='Enable bitcode for iOS targets. On debug runtime modes, this will be a marker only.')
-
-  parser.add_argument('--stripped', default=True, action='store_true',
-                      help='Strip debug symbols from the output. This defaults to true and has no effect on iOS.')
+  parser.add_argument(
+      '--out-dir',
+      default='',
+      type=str,
+      help='Root out directory. Target specific gn files will be generated in ${out-dir}/'
+  )
+  parser.add_argument(
+      '--target-dir',
+      default='',
+      type=str,
+      help='Use the specified name for target out directory. By default this tool determines one.'
+  )
+
+  parser.add_argument(
+      '--full-dart-sdk',
+      default=False,
+      action='store_true',
+      help='include trained dart2js and dartdevc snapshots. Enable only on steps that create an SDK'
+  )
+  parser.add_argument(
+      '--no-full-dart-sdk', dest='full_dart_sdk', action='store_false'
+  )
+
+  parser.add_argument(
+      '--ide',
+      default='',
+      type=str,
+      help='The IDE files to generate using GN. Use `gn gen help` and look for the --ide flag to'
+      +
+      ' see supported IDEs. If this flag is not specified, a platform specific default is selected.'
+  )
+
+  parser.add_argument(
+      '--allow-deprecated-api-calls',
+      action='store_true',
+      default=False,
+      help='Turns off warnings about the usage of deprecated APIs.'
+  )
+
+  parser.add_argument(
+      '--disable-desktop-embeddings',
+      default=False,
+      action='store_true',
+      help='Do not include desktop embeddings in the build.'
+  )
+  parser.add_argument(
+      '--build-glfw-shell',
+      action='store_const',
+      const=True,
+      help='Build the GLFW shell on supported platforms where it is not built by default.'
+  )
+  parser.add_argument(
+      '--no-build-glfw-shell',
+      dest='build_glfw_shell',
+      action='store_const',
+      const=False,
+      help='Do not build the GLFW shell on platforms where it is built by default.'
+  )
+  parser.add_argument(
+      '--build-embedder-examples',
+      action='store_const',
+      const=True,
+      help='Build the example embedders using the Embedder API.'
+  )
+  parser.add_argument(
+      '--no-build-embedder-examples',
+      dest='build_embedder_examples',
+      action='store_const',
+      const=False,
+      help='Do not build the example embedders using the Embedder API.'
+  )
+
+  parser.add_argument(
+      '--bitcode',
+      default=False,
+      action='store_true',
+      help='Enable bitcode for iOS targets. On debug runtime modes, this will be a marker only.'
+  )
+
+  parser.add_argument(
+      '--stripped',
+      default=True,
+      action='store_true',
+      help='Strip debug symbols from the output. This defaults to true and has no effect on iOS.'
+  )
   parser.add_argument('--no-stripped', dest='stripped', action='store_false')
 
-  parser.add_argument('--prebuilt-dart-sdk', default=True, action='store_true',
-                      help='Whether to use a prebuilt Dart SDK instead of building one. This defaults to ' +
-                      'true and is enabled on CI.')
-  parser.add_argument('--no-prebuilt-dart-sdk', dest='prebuilt_dart_sdk', action='store_false')
-
-  parser.add_argument('--fuchsia-target-api-level', dest='fuchsia_target_api_level')
-
-  parser.add_argument('--support-fractional-translation', dest='support_fractional_translation', default=False,
-                      action='store_true', help='Whether to allow layers to render at fraction pixel '
-                      'boundaries.')
+  parser.add_argument(
+      '--prebuilt-dart-sdk',
+      default=True,
+      action='store_true',
+      help='Whether to use a prebuilt Dart SDK instead of building one. This defaults to '
+      + 'true and is enabled on CI.'
+  )
+  parser.add_argument(
+      '--no-prebuilt-dart-sdk', dest='prebuilt_dart_sdk', action='store_false'
+  )
+
+  parser.add_argument(
+      '--fuchsia-target-api-level', dest='fuchsia_target_api_level'
+  )
+
+  parser.add_argument(
+      '--support-fractional-translation',
+      dest='support_fractional_translation',
+      default=False,
+      action='store_true',
+      help='Whether to allow layers to render at fraction pixel '
+      'boundaries.'
+  )
 
   # Flags for Dart features.
-  parser.add_argument('--use-mallinfo2', dest='use_mallinfo2', default=False, action='store_true',
-                      help='Use mallinfo2 to collect malloc stats.')
+  parser.add_argument(
+      '--use-mallinfo2',
+      dest='use_mallinfo2',
+      default=False,
+      action='store_true',
+      help='Use mallinfo2 to collect malloc stats.'
+  )
 
   # Impeller flags.
-  parser.add_argument('--enable-impeller-playground', default=False, action='store_true',
-                      help='Whether impeller unit tests run in playground mode.')
-  parser.add_argument('--prebuilt-impellerc', default=None, type=str,
-                      help='Absolute path to a prebuilt impellerc. ' +
-                      'Do not use this outside of CI or with impellerc from a different engine version.')
+  parser.add_argument(
+      '--enable-impeller-playground',
+      default=False,
+      action='store_true',
+      help='Whether impeller unit tests run in playground mode.'
+  )
+  parser.add_argument(
+      '--prebuilt-impellerc',
+      default=None,
+      type=str,
+      help='Absolute path to a prebuilt impellerc. ' +
+      'Do not use this outside of CI or with impellerc from a different engine version.'
+  )
 
   # Sanitizers.
   parser.add_argument('--asan', default=False, action='store_true')
@@ -643,24 +852,29 @@ def parse_args(args):
   parser.add_argument('--tsan', default=False, action='store_true')
   parser.add_argument('--ubsan', default=False, action='store_true')
 
-  parser.add_argument('--trace-gn', default=False, action='store_true',
-                       help='Write a GN trace log (gn_trace.json) in the Chromium tracing format in the build directory.')
+  parser.add_argument(
+      '--trace-gn',
+      default=False,
+      action='store_true',
+      help='Write a GN trace log (gn_trace.json) in the Chromium tracing format in the build directory.'
+  )
 
   # Verbose output.
   parser.add_argument('--verbose', default=False, action='store_true')
 
   return parser.parse_args(args)
 
+
 def main(argv):
   args = parse_args(argv)
 
   exe = '.exe' if sys.platform.startswith(('cygwin', 'win')) else ''
 
   command = [
-    '%s/flutter/third_party/gn/gn%s' % (SRC_ROOT, exe),
-    'gen',
-    '--check',
-    '--export-compile-commands',
+      '%s/flutter/third_party/gn/gn%s' % (SRC_ROOT, exe),
+      'gen',
+      '--check',
+      '--export-compile-commands',
   ]
 
   if args.ide != '':
@@ -696,5 +910,6 @@ def main(argv):
 
   return gn_call_result
 
+
 if __name__ == '__main__':
-    sys.exit(main(sys.argv))
+  sys.exit(main(sys.argv))