28513 Revert “Add benchmarks to measure dart -> native time (#28492)” (cla: yes)

28514 RTM must acquire lock before called IsMergedUnsafe (cla: yes, needs tests)

28515 Roll Skia from a0d61eb56199 to 51f95129285f (5 revisions) (cla: yes, waiting for tree to go green)

28517 Roll Fuchsia Mac SDK from cDn94pEla… to YnuT0nBZG… (cla: yes, waiting for tree to go green)

28520 [flutter_releases] apply patches to flutter-2.5-candidate.8 (platform-ios, platform-android, cla: yes, platform-fuchsia, embedder)