This contains a fix needed to build with the latest Clang toolchain.

[Re-land] Add SPIR-V FragmentShader API to painting.dart

- Add a SPIR-V FragmentShader interface in painting.dart
- Create end to end pixel tests for ops supported by the SPIR-V to SkSL transpiler
- The end to end tests also test the c++ fragment shader implementation
Co-authored-by: NChristopher Crawford <chriscraws@gmail.com>

This reverts commit a116cc0d.

This reverts commit 6d6ce343.

* 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 

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