7439 Remove legacy and deprecated defaultClipBehavior (cla: yes)

7442 Move Picture.toImage rasterization to the GPU thread (cla: yes)

7443 Avg ms/frame instead of FPS in performance overlay (cla: yes)

7444 Pass deadline to embedder idle notification callback (cla: yes)

7445 Use anti-aliasing when drawing text in the performance overlay (cla: yes)

7446 Reland Dart SDK rolls made since 2019/01/08 (cla: yes)

7447 Make SetLocales more consistent with other RuntimeController methods (cla: yes)

7449 Dart SDK roll for 2019-01-11 (cla: yes)

7450 Stop pumping frames in applicationWillResignActive (cla: yes)