12328 Added javadoc comments to FlutterActivity and FlutterFragmentActivity. (cla: yes)

12330 Ensure DRRects without corners also draw. (cla: yes)

12335 [Web] Implement dark mode support for web (cla: yes)

12336 Check for index bounds in RTL handling for trailing whitespace runs. (cla: yes)

12338 Add missing CL, fix targets for Fuchsia (cla: yes)

12340 [flutter_runner] Do not use pre-builts just yet (cla: yes)

12342 Update test to verify that secondary isolate gets shutdown before root isolate exits. (cla: yes)

12343 [flutter_runner] Remove usages of shared snapshots from CC sources (cla: yes)