15956 Prevent duplicate plugin registration in FlutterEnginePluginRegistry. (#49365) (affects: add-to-app, cla: yes)

15957 Roll src/third_party/skia c88a3bc3f561..a7e557f3e353 (6 commits) (autoroller: commit, cla: yes)

15958 [fuchsia] Expose view_ref as part of dart:fuchsia initialization (cla: yes)

15959 Roll src/third_party/dart 3eaae5405d37..c359b5943a52 (13 commits) (autoroller: commit, cla: yes)