D3D11: Clean up blendState code. Masked Clear Draw Changes: - Use universal blendstate object - Eliminate blendState cache for masked clears - Use rasterState and scissor rect for scissoring instead of adjusting vertex positions - VB contains only static position data (per vertex color removed) - Clear color(s) and depth clear values now passed in using a constant buffer - MultiColorclear shader used for float clears to workaround alpha rounding issues - Update shader compile script and shader source and bytecode headers - Remove unused shaders (source and bytecode headers) - Use com pointers where possible for D3D11 objects BUG=angleproject:1632 Change-Id: I98e38451bd453f53b772fe93ec9dcceb4196ea58 Reviewed-on: https://chromium-review.googlesource.com/413736 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahmeer Esmail <shahmeer.esmail@intel.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>