8646 Disable auth codes for Observatory test (cla: yes)

8649 Roll buildroot to 380d0ed5c3399d5a2aaac4a66d98e3a3fda77c31 (cla: yes)

8652 Add factory methods to FileMapping that make it easy to create common mappings. (cla: yes)

8653 Cleanup references to FLX archives from the engine. (cla: yes)

8656 Only allow mappings for ICU initialization. (cla: yes)

8657 Change Vertices.indices to use a Uint16 list to more accurately reflect Skia’s API (cla: yes)

8658 Allow native bindings in secondary isolates. (cla: yes)

8659 Replace ThreadLocal with ThreadLocalUniquePtr (cla: yes)