21938 Roll Dart SDK from b58cfe5ab24e to aaab579579be (1 revision) (cla: yes, waiting for tree to go green)

21940 Reformat some files that were not auto-formatted (cla: yes, platform-android, waiting for tree to go green)

21941 Add FML_UNREACHABLE to declare points in code that should never be reached. (cla: yes, waiting for tree to go green)

21944 Roll Fuchsia Mac SDK from _FaRRt69Z… to XZSNobQCT… (cla: yes, waiting for tree to go green)

21946 Roll Dart SDK from aaab579579be to 42a0bf548ea3 (1 revision) (cla: yes, waiting for tree to go green)