39282 Expose text metrics in TextPainter. (cla: yes, framework)

39286 Update docs for GrowthDirection and scrollOffset (cla: yes, d: api docs, framework, waiting for tree to go green)

39289 CupertinoActivityIndicator & CupertinoApp dark mode (cla: yes, f: cupertino, framework)

39299 Add showAboutDialog sample (cla: yes, f: material design, framework)

39300 Add smoke tests for Catalina/Android testing. (cla: yes, team)

39312 let flutter build aar use a local engine (cla: yes, tool)

39333 Allow independent theming of Persistent and Modal bottom sheets Background Color (cla: yes, f: material design, framework)