skia: Make the validate match interface for *_draw_instanced

For whatever reason, on the Mac, the command buffer is reporting
ARB_draw_instanced as a valid extension. This is probably a bug in the
command buffer and I'll look into this later.

In Skia, we don't check for ARB_draw_instanced in GLES2 when building
the interface, but during the validate, we do, so we ended up failing
the validation.

Looking a bit further at the specs, ARB_draw_instanced is GL only,
whereas EXT_draw_instanced is both GL and GLES.  I've updated the code
to reflect this.

See:
https://cvs.khronos.org/svn/repos/ogl/trunk/doc/registry/public/specs/ARB/draw_instanced.txt
https://www.opengl.org/registry/specs/EXT/draw_instanced.txt

Everything above also applies to ARB/EXT_instanced_arrays

https://www.khronos.org/registry/gles/extensions/EXT/EXT_instanced_arrays.txt
https://www.opengl.org/registry/specs/ARB/instanced_arrays.txt

Review URL: https://codereview.chromium.org/1409053003
2 files changed