18252 Roll src/third_party/dart 017b1c46f6d5..518f09726660 (2 commits) (cla: yes, waiting for tree to go green)

18253 Use ‘message’ as the parameter name in FlMessageCodec::encode_message (cla: yes)

18255 Restore integer snapping on OpacityLayer (cla: yes, perf: speed, severe: performance)

18257 Restore the call to initConfig in FlutterLoader (cla: yes)

18259 Roll src/third_party/dart 518f09726660..092ed38a87e9 (3 commits) (cla: yes, waiting for tree to go green)