71944 app bar leading back button should not change if the route is popped (cla: yes, f: material design, framework, waiting for tree to go green)

72014 [flutter_releases] Flutter Framework Stable 1.22.5 Cherrypicks (a: tests, cla: yes, d: examples, engine, f: cupertino, f: material design, framework, team, tool)

72040 Prepare to migrate API doc samples and snippets to null safety (cla: yes, f: cupertino, f: material design, framework, team, waiting for tree to go green)

72043 Deprecate maxLengthEnforced for text fields (cla: yes, f: cupertino, f: material design, framework)