29793 Revert 29789 revert 29542 freiling view ref (cla: yes, waiting for tree to go green, platform-fuchsia, needs tests)

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

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

29816 Mentioned that replies can be invoked on any thread (platform-android, cla: yes, waiting for tree to go green, needs tests)

29819 Run Dart VM tasks on the engine’s ConcurrentMessageLoop instead the VM’s separate thread pool. (cla: yes, needs tests)

29824 Windows: Clean up FML file debug messages (cla: yes, waiting for tree to go green, needs tests)