29798 Stopped creating the shell inside of a sync_switch when spawning. (cla: yes, needs tests)

29799 Roll Skia from e136c31fe49d to 688cb15faa64 (11 revisions) (cla: yes, waiting for tree to go green)

29800 Listen for display refresh changes and report them correctly (platform-ios, platform-android, cla: yes, waiting for tree to go green, embedder)

29801 [web] move browser installation to BrowserEnvironment.prepare (cla: yes, platform-web, needs tests)

29803 Roll Dart SDK from 7d957c006c4f to 91e3fa160432 (2 revisions) (cla: yes, waiting for tree to go green)