GL: Mark unused uniform locations that were explicitly bound as ignored If a uniform location is unused, but a call to glBindUniformLocation has explicitly bound the uniform, ANGLE validation still treated the uniform as unused and returned errors. The correct behavior is to ignore the uniform and silently fail. Bug: angleproject:4374 Change-Id: Ic7b97f23cf8bc2d5380129322595e51b3d4a9fcc Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2036676 Commit-Queue: Jonah Ryan-Davis <jonahr@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>