21656 Roll Fuchsia Mac SDK from xM2vYLfIT… to m6w8tDXMm… (cla: yes)

21660 Run desktop darwin tests in debug mode (cla: yes, waiting for tree to go green)

21663 Store selection base/extent as size_t (affects: text input, cla: yes, platform-linux, platform-windows)

21665 Ensure JNI is not called from raster thread (cla: yes, platform-android, waiting for tree to go green)

21666 Roll Skia from 107114dd1d6e to a7f69c290667 (18 revisions) (cla: yes)

21668 Remove dependencies on _product variants of libdart from the Fuchsia release mode build (cla: yes)