There are some important things to do when pulling in a new revision of ANGLE.

1. Add a note explaining that we are explicitly choosing the non-GPL license for distributing sources based on Bison 2.4+. Add the following text: "* Apple Note: For the avoidance of doubt, Apple elects to distribute this file under the terms of the BSD license." to the files:
   • glslang_tab.cpp
   • glslang_tab.h
   • ExpressionParser.cpp
2. Update ANGLE.plist with the details of the version of ANGLE you are committing.
3. Add preprocessor comments to allow ANGLE to build on older versions of clang. Basically, copy ​this commit