13153 Make the Dart isolate constructor private.

13154 Fix an output file path for the frontend server package_incremental script

13157 Fix type error in SkVertices

13159 Move surface-based SceneBuilder implementation under surface/

13162 Document //flutter/runtime/dart_isolate.h

13175 Remove redundant call to updateEditingState in sendKeyEvent

13176 Add repeatCount to FlutterKeyEvent

13177 Update compiler to Clang 10.

13182 If we get a ‘down’ event, add that device to the active devices.

13185 Adding firefox_installer.dart

13192 Use window.devicePixelRatio in the CanvasKit backend