82028 Fix dartdoc for SliverAppBar#shadowColor (framework, f: material design, cla: yes)

82057 Migrate to ChannelBuffers.push (a: tests, team, framework, f: material design, a: accessibility, cla: yes, f: cupertino, d: examples, waiting for tree to go green)

82084 Enable unnecessary_null_checks lint (a: tests, team, tool, framework, f: material design, cla: yes, f: cupertino, waiting for tree to go green)

82152 Fix slider notifies start and end twice when participates in gesture arena (framework, f: material design, cla: yes, waiting for tree to go green)

82196 Deprecated ThemeData buttonColor (framework, f: material design, cla: yes)