27567 [web] use a different method for launching desktop safari (cla: yes, platform-web, needs tests)

27569 Extract the prebuilt Dart SDK to a temp directory and then move it after the extraction completes (cla: yes)

27572 Roll Fuchsia Mac SDK from 897eI2xwc… to rQOi2N8BM… (cla: yes, waiting for tree to go green)

27573 Roll Skia from 946a4cb8acb7 to 38a6e5aa1a49 (8 revisions) (cla: yes, waiting for tree to go green)

27574 Roll Skia from 38a6e5aa1a49 to 2373b9ed9617 (1 revision) (cla: yes, waiting for tree to go green)