72316 Remove Scrollbar.isAlwaysShown assert based on Scrollbar.controller (a: quality, cla: yes, f: cupertino, f: material design, f: scrolling, framework, severe: new feature, waiting for tree to go green)

72344 Add BuildContext parameter to TextEditingController.buildTextSpan (cla: yes, f: material design, framework, waiting for tree to go green)

72431 Fixes: “FloatingActionButton.extended’s isExtended property if false should show icon, not label” (cla: yes, f: material design, framework)

72472 Added backwardsCompatibility flag to AppBarTheme (cla: yes, f: material design, framework, waiting for tree to go green)

72477 Updated the MaterialBanner example, NNBD, etc (cla: yes, f: material design, framework, waiting for tree to go green)