This is to minimize the number of environment variables being passed to
scripts from recipes.

* fuchsia: Add scaffolding for flatland migration

* fuchsia: Add ViewProvider based view creation logic and basic present loop

Add SPIR-V FragmentShader API to painting.dart 

The script has not been ported to Python 3.  The environment required by
Python 3 (e.g. PYTHONHOME) may conflict with the environment expected by
the Python 2 runtime linked into the version of GDB launched by the script.

Fixes for Embedder and RefCounted tests.

- Fix dead character crashes the channel handler.
- Fix dead key messages are redispatched, making the message a regular character message.

This reverts commit 589b6a20.