84145 Migrate integration_tests/channels to null safety (team, framework, cla: yes, waiting for tree to go green, a: null-safety, tech-debt)

84171 Remove duplicate code in conditional expressions (framework, cla: yes, waiting for tree to go green)

84182 Add RotatedBox Widget of the Week video to documentation (framework, cla: yes, d: api docs, waiting for tree to go green, documentation)

84187 Revert “Always push layer for RenderAnimatedOpacityMixin” (framework, cla: yes)

84256 alignment of doc comments and annotations (a: tests, team, tool, framework, a: internationalization, cla: yes, f: cupertino, waiting for tree to go green)

84257 fix a PlatformView gesture bug (e: device-specific, framework, cla: yes, f: gestures, waiting for tree to go green)