78284 Add CupertinoScrollbar api docs (framework, cla: yes, f: cupertino, d: api docs, d: examples, waiting for tree to go green, documentation)

79669 Reland the Dart plugin registry (team, tool, cla: yes, d: examples, waiting for tree to go green)

80600 Standardize how Java8 is set in gradle files (team, tool, a: accessibility, cla: yes, d: examples, waiting for tree to go green)

80908 migrate from jcenter to mavencentral (team, tool, cla: yes, d: examples)

81226 Revert “Migrate to ChannelBuffers.push” (a: tests, team, framework, f: material design, a: accessibility, cla: yes, f: cupertino, d: examples)