[iOS] switch iOS to slimpeller variant.

[jonahwilliams]

Now that skia can no longer be used on both iOS devices and Simulators, we can switch the iOS engine to the "slimpeller" variant which removes some (not all!) of the Skia dependencies. This should reduce binary size and build time.

I also did some cleanups as some tests we're still opting into Skia behaviors (though not actually running skia) and we now flag these as errors.

[jmagman]

🎉

The iOS scenario tests used run twice, once with Impeller and then again with "Skia" (I guess both Impeller now), looks like you got some of it in flutter/engine#56706 but there's still a few things to clean up:

flutter/engine/src/flutter/testing/ios_scenario_app/bin/run_ios_tests.dart

Line 135 in 7d23780

if (withImpeller) {

https://github.com/flutter/flutter/blob/master/engine/src/flutter/testing/ios_scenario_app/ios/Scenarios/Scenarios/Info_Skia.plist

You could also file an issue and I can look.

[jmagman]

This should reduce binary size and build time.

Is this the benchmark test to watch for binary size?

https://flutter-flutter-perf.luci.app/e/?queries=sub_result%3Dflutter_framework_uncompressed_bytes&selected=commit%3D2801225%26name%3D%252Carch%253Darm%252Cbranch%253Dmaster%252Cconfig%253Ddefault%252Cdevice_type%253DiPhone_11%252Cdevice_version%253Dnone%252Chost_type%253Dmac%252Csub_result%253Dflutter_framework_uncompressed_bytes%252Ctest%253Dhello_world_ios__compile%252C

[jonahwilliams]

That looks about right. We also have release_size_bytes: https://flutter-flutter-perf.luci.app/e/?queries=device_type%3DiPhone_11%26sub_result%3Drelease_size_bytes&selected=commit%3D2801195%26name%3D%252Carch%253Darm%252Cbranch%253Dmaster%252Cconfig%253Ddefault%252Cdevice_type%253DiPhone_11%252Cdevice_version%253Dnone%252Chost_type%253Dmac%252Csub_result%253Drelease_size_bytes%252Ctest%253Dimitation_game_flutter__compile%252C which might be the whole thing?

[jonahwilliams]

From looking at the CI config I don't think we're running it twice anymore, just three times instead:

• ios_debug_unopt_sim
• ios_debug_unopt_sim_arm64
• ios_debug_unopt_sim_arm64_extension_safe

If that isn't expected let me know and I'll file a bug. I don't see two invocations per target though, just one.

[chinmaygarde]

🎉