72829 Migrate some sample code to NNBD [3] (a: null-safety, cla: yes, d: api docs, d: examples, documentation, f: cupertino, framework, team, waiting for tree to go green)

73044 [Api docs]Added dartpad demo for Bottom App Bar (cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

73247 Fixed typo in icon theme (cla: yes, documentation, framework, waiting for tree to go green)

73761 add a readme for the dart fix tests (cla: yes, documentation, framework)

platform-mac - 22 pull request(s)

68050 Run Xcode command lines tools in native ARM (cla: yes, platform-mac, tool)