21832 Roll Fuchsia Mac SDK from 8Cb2zG9e3… to SFNhlfVb_… (cla: yes, waiting for tree to go green)

21834 Roll Skia from 7bbdde059685 to 99446001182c (5 revisions) (cla: yes, waiting for tree to go green)

21839 [android] Refactor surface factory and wire in external view embedder (cla: yes, platform-android, waiting for tree to go green)

21846 Roll Dart SDK from 4226116043f5 to 04cf6ade9fc4 (4 revisions) (cla: yes, waiting for tree to go green)