This reverts commit 786ad387.

Reason for revert: 
Seems to have a bug with binding the BlendStates, causing a crash on
Intel.

https://luci-milo.appspot.com/buildbot/chromium.gpu.fyi/Win10%20Release%20%28Intel%20HD%20530%29/141

Failing WebGL 2 tests
WebglConformance_conformance2_reading_read_pixels_from_fbo_test
WebglConformance_deqp_functional_gles3_readpixel

Also generates D3D11 runtime warnings:
D3D11 ERROR: ID3D11DeviceContext::Draw: The renderTarget bound to slot 0 has a format (R8_UINT) that does not support blending. The Pixel Shader output signature indicates this output could be written, and the Blend State indicates blending is enabled for this slot. [ EXECUTION ERROR #376: DEVICE_DRAW_OM_RENDER_TARGET_DOES_NOT_SUPPORT_BLENDING]

BUG=angleproject:1632
BUG=chromium:688419

Original change's description:
> 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>
> 

TBR=geofflang@chromium.org,jmadill@chromium.org,shahmeer.esmail@intel.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=angleproject:1632

Change-Id: Iea537505d8cce7241edaba1f1d9f404abb1d9a10
Reviewed-on: https://chromium-review.googlesource.com/437306Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>