18865 Add a deprecation note to FlutterFragmentActivity (cla: yes, platform-android)

18866 onBeginFrame JNI (cla: yes, platform-android, waiting for tree to go green)

18867 onEndFrame JNI (cla: yes, platform-android, waiting for tree to go green)

18868 Roll Fuchsia Linux SDK from DELkx… to j9T0m… (cla: yes, waiting for tree to go green)

18869 Roll Fuchsia Mac SDK from b4Gyr… to JVQxV… (cla: yes, waiting for tree to go green)

18871 Roll Dart SDK from 578fa6bee9eb to 4b9c2356e962 (1 revision) (cla: yes, waiting for tree to go green)