27355 Roll Dart SDK from fb3ebe02a0bb to 2b81a20ef985 (8 revisions) (cla: yes, waiting for tree to go green)

27366 Roll Dart SDK from 2b81a20ef985 to 3c094fbf2093 (1 revision) (cla: yes, waiting for tree to go green)

27367 Fix dart analysis (cla: yes, waiting for tree to go green, needs tests)

27370 refactor and simplify CI dart analysis (cla: yes, waiting for tree to go green)

27371 Set ANDROID_HOME in run_gradle.py (cla: yes, waiting for tree to go green)