M(ulti-platform)ANGLE effort

Starting in early 2014, the ANGLE team has begun work on refactoring the code with the goal of supporting translation to desktop OpenGL. In 2016, work on supporting Vulkan as a back-end started. The new purpose of ANGLE is to provide a consistent OpenGL ES and EGL context on as many platforms as possible.

The design doc is available [here] (https://docs.google.com/document/d/17mxRfzXuEWyvGM3t2KqVY4svvfRj_GzysOEpmnDpqeo/edit?usp=sharing).