18895 Roll Dart SDK from 66e2b22d14af to df435c923544 (1 revision) (cla: yes, waiting for tree to go green)

18896 Roll Skia from f9ffdd6942f9 to 6e659e960945 (1 revision) (cla: yes, waiting for tree to go green)

18897 Roll Fuchsia Mac SDK from uCq3V… to f9ILa… (cla: yes, waiting for tree to go green)

18898 Remove simulator build mode restrictions (cla: yes, waiting for tree to go green)

18901 Remove pipeline in favor of layer tree holder (cla: yes)

18903 Put JNI functions under an interface (cla: yes, platform-android)