21805 Roll Skia from fa8891164062 to 01b93eabe25b (4 revisions) (cla: yes, waiting for tree to go green)

21806 Forward Error objects to uncaught exception handler if there is one. (cla: yes, platform-android)

21807 [web] enabling firefox screenshot tests. adding to documentation (cla: yes)

21808 Roll Dart SDK from e256855d07ba to a3b62f366529 (4 revisions) (cla: yes, waiting for tree to go green)

21809 Roll Dart SDK from e256855d07ba to a3b62f366529 (4 revisions) (cla: yes, waiting for tree to go green)