21917 Roll Skia from 839fb228ac44 to 418eda2c599a (9 revisions) (cla: yes, waiting for tree to go green)

21918 Break the reference cycle between the surface factory and the external view embedder (cla: yes, platform-android)

21919 Roll Dart SDK from e655b9a3839e to b58cfe5ab24e (1 revision) (cla: yes, waiting for tree to go green)

21920 Roll Dart SDK from e655b9a3839e to b58cfe5ab24e (1 revision) (cla: yes, waiting for tree to go green)

21921 Update FLUTTER_NOLINT uses to include issue link (cla: yes, code health)