12253 Implement Base32Decode (cla: yes)

12255 Roll dart to d9489622befb638c040975163cf9b8eba2ff057b. (cla: yes)

12256 Do not assume Platform.script is a Dart source file during training. (cla: yes)

12257 Re-enable ThreadChecker and fix associated failures (CQ+1, cla: yes)

12258 Refactor and polish the ‘felt’ tool (cla: yes)

12263 Revert “Started taking advantage of Skia’s new copyTableData to avoid (#10154)” (cla: yes)

12264 Revert “Add some AppLifecycleTests (#11890)” (cla: yes)