22265 Roll Dart SDK from 52783837369d to b43baaaa477d (723 revisions) (cla: yes, waiting for tree to go green)

22269 Roll Dart SDK from b43baaaa477d to a4fbabcd73dc (1 revision) (cla: yes, waiting for tree to go green)

22270 Fix code style issues in MacOS embedder (cla: yes, waiting for tree to go green)

22271 Roll Fuchsia Mac SDK from 6yEx5GNGG… to o45EAhxJZ… (cla: yes, waiting for tree to go green)

22272 Remove GetExternalViewEmbedder from surface (cla: yes, platform-android, platform-ios, waiting for tree to go green)