8864 Add resize functions to GLFW shell (cla: yes)

8867 Prevent redundant layouts when floor(width) is the same (cla: yes)

8869 Wire up Fuchsia SDK related updated for shell dependencies. (cla: yes)

8870 Roll buildroot to pull in Fuchsia SDK flag updates. (cla: yes)

8871 Copy //runtime/dart/utils from Topaz into the engine. (cla: yes)

8873 Synthesize buttons for embedders (cla: yes)

8881 Log instead of throwing (cla: yes)

8884 Copy //dart-pkg/zircon

fuchsia from Topaz into the engine. (cla: yes)

8886 Copy the Flutter Runner from //topaz into the engine. (cla: yes)