11421 sync Flutter Web engine to the latest (cla: yes)

11423 Add tracing of the number of frames in flight in the pipeline. (cla: yes)

11427 Skip empty platform view overlays. (cla: yes)

11436 update method for skia (cla: yes)

11441 Android 10+ View.setSystemGestureExclusionRects (cla: yes, platform-android)

11449 Roll buildroot and update gn script for bitcode_marker (cla: yes)

11451 Android 10+ View.getSystemGestureExclusionRects (cla: yes, platform-android)

11456 Update the ui.LineMetrics.height metric to be more useful to external users (cla: yes)