Remove reliance on linked in GL functions for assembling GLES interfaces.

Make Android pull in gl2.h directly to workaround broken eglGetProcAddress for unextended GLES2 functions.

Use interface assembler for angle and iOS.

R=robertphillips@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/500153002
10 files changed