Program: Add cache samplers and type masks. This mask cleans up some of the iteration logic in State::syncProgramTextures. It will make it easier to optimize this function in the future. This will also make it easier to recompute the sampler type validation. Leads to a 5% improvement in State::syncProgramTextures. Bug: angleproject:2747 Bug: angleproject:2763 Change-Id: Ic9a555df843ad23b4c562e6e4a2d425bee58a856 Reviewed-on: https://chromium-review.googlesource.com/1164306 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>