27970 Python 3 compatibility fix for running Java tests using run_tests.py (cla: yes)

27971 Engine build configuration for web engine. (cla: yes)

27972 Fix: modifier keys not recognized on macOS Web (cla: yes, platform-web, cp: 2.5)

27974 added log statement to timerfd_settime failure (cla: yes, needs tests)

27975 Enable Dart compressed pointers for 64-bit mobile targets (cla: yes)

27976 Roll Dart SDK from 749ee4e9e053 to defd2ae02a3f (2 revisions) (cla: yes, waiting for tree to go green)

27977 [canvaskit] Release overlays to the cache once they have been used (cla: yes, platform-web)