We we're unable to cleanup the unused uniforms if we did not keep
a list of them while parsing them in ProgramLinkResource. Now
that we keep a history of them, we're able to clean them up and
fix a few dEQP tests.

Bug: angleproject:2582
Bug: angleproject:2585
Bug: angleproject:2587
Bug: angleproject:2589
Bug: angleproject:2590
Bug: angleproject:2593

Change-Id: Ic1f9151e356a3d05e83f1031cc7b187b370284e5
Reviewed-on: https://chromium-review.googlesource.com/1085644
Commit-Queue: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>