27295 Fix the firebase scenario app run and assert that it does good things (platform-android, cla: yes, waiting for tree to go green, needs tests)

27296 [web] Librarify all remaining files (cla: yes, platform-web, needs tests)

27311 Windows: Implement GetPreferredLanguages for UWP and support l18n (cla: yes, platform-windows, needs tests)

27321 Fix import order to unblock Dart roll (cla: yes, needs tests)

27330 [fuchsia] Cleanup unused method in dart:zircon handle (cla: yes, waiting for tree to go green, platform-fuchsia, needs tests)

27332 Make FlutterFragment usable without requiring it to be attached to an Android Activity. (platform-android, cla: yes, waiting for tree to go green, needs tests)