Actually use Impeller in scenario_app tests

testing/scenario_app/android/BUILD.gn

@@ -7,7 +7,6 @@ import("//flutter/testing/rules/android.gni")
 _android_sources = [
   "app/build.gradle",
   "app/src/androidTest/java/dev/flutter/TestRunner.java",
-  "app/src/androidTest/java/dev/flutter/scenarios/EngineLaunchE2ETest.java",
   "app/src/androidTest/java/dev/flutter/scenarios/ExampleInstrumentedTest.java",
   "app/src/androidTest/java/dev/flutter/scenariosui/DrawSolidBlueScreenTest.java",
   "app/src/androidTest/java/dev/flutter/scenariosui/ExternalTextureTests.java",

testing/scenario_app/android/app/src/androidTest/java/dev/flutter/TestRunner.java

@@ -8,10 +8,21 @@
 import androidx.annotation.Nullable;
 import androidx.test.runner.AndroidJUnitRunner;
 import dev.flutter.scenariosui.ScreenshotUtil;
+import io.flutter.FlutterInjector;
 
 public class TestRunner extends AndroidJUnitRunner {
   @Override
   public void onCreate(@Nullable Bundle arguments) {
+    String[] engineArguments = null;
+    if ("true".equals(arguments.getString("enable-impeller"))) {
+      // Set up the global settings object so that Impeller is enabled for all tests.
+      engineArguments = new String[] {"--enable-impeller=true"};
+    }
+    // For consistency, just always initilaize FlutterJNI etc.
+    FlutterInjector.instance().flutterLoader().startInitialization(getTargetContext());
+    FlutterInjector.instance()
+        .flutterLoader()
+        .ensureInitializationComplete(getTargetContext(), engineArguments);
     ScreenshotUtil.onCreate();
     super.onCreate(arguments);
   }

testing/scenario_app/bin/run_android_tests.dart

@@ -190,6 +190,7 @@ Future<void> _run({
 
   late Process logcatProcess;
   late Future<int> logcatProcessExitCode;
+  bool seenImpeller = false;
 
   final IOSink logcat = File(logcatPath).openWrite();
   try {
@@ -212,6 +213,9 @@ Future<void> _run({
       logcatOutput.listen((String line) {
         // Always write to the full log.
         logcat.writeln(line);
+        if (enableImpeller && !seenImpeller) {
+          seenImpeller = line.contains('Using the Impeller rendering backend');
+        }
 
         // Conditionally parse and write to stderr.
         final AdbLogLine? adbLogLine = AdbLogLine.tryParse(line);
@@ -316,11 +320,13 @@ Future<void> _run({
         'am',
         'instrument',
         '-w',
-        if (smokeTestFullPath != null) '-e class $smokeTestFullPath',
-        'dev.flutter.scenarios.test/dev.flutter.TestRunner',
-        if (enableImpeller) '-e enable-impeller',
+        if (smokeTestFullPath != null)
+          '-e class $smokeTestFullPath',
+        if (enableImpeller)
+          '-e enable-impeller true',
         if (impellerBackend != null)
           '-e impeller-backend ${impellerBackend.name}',
+        'dev.flutter.scenarios.test/dev.flutter.TestRunner',
       ]);
       if (exitCode != 0) {
         panic(<String>['instrumented tests failed to run']);
@@ -348,6 +354,16 @@ Future<void> _run({
       log('wrote logcat to $logcatPath');
     });
 
+    if (enableImpeller) {
+      await step('Validating Impeller...', () async {
+        if (!seenImpeller) {
+          panic(<String>[
+            '--enable-impeller was specified, but Impeller was not used.',
+          ]);
+        }
+      });
+    }
+
     await step('Symbolize stack traces', () async {
       final ProcessResult result = await pm.run(
         <String>[

testing/scenario_app/lib/main.dart

@@ -25,19 +25,14 @@ void main() {
   channelBuffers.setListener('driver', _handleDriverMessage);
   channelBuffers.setListener('write_timeline', _handleWriteTimelineMessage);
 
-  // TODO(matanlurey): https://github.com/flutter/flutter/issues/142746.
-  // This Dart program is used for every test, but there is at least one test
-  // (EngineLaunchE2ETest.java) that does not create a FlutterView, so the
-  // implicit view's size is not initialized (and the assert would be tripped).
-  //
-  // final FlutterView view = PlatformDispatcher.instance.implicitView!;
+  final FlutterView view = PlatformDispatcher.instance.implicitView!;
   // Asserting that this is greater than zero since this app runs on different
   // platforms with different sizes. If it is greater than zero, it has been
   // initialized to some meaningful value at least.
-  // assert(
-  //   view.display.size > Offset.zero,
-  //   'Expected ${view.display} to be initialized.',
-  // );
+  assert(
+    view.display.size > Offset.zero,
+    'Expected ${view.display} to be initialized.',
+  );
 
   final ByteData data = ByteData(1);
   data.setUint8(0, 1);