This will enable more caching for ValidateDrawAttribs. It requires some
minor refactoring of the GLES 1 code.

Bug: angleproject:1391
Change-Id: I52b73c9384d14cdb90ba6337bfc1ab345866fff0
Reviewed-on: https://chromium-review.googlesource.com/1147436
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>