Attach GrOptDrawState into shader building pipeline

The OptDrawState is now used for creating the actual gl shader. Current
optimizations dones in GrOptDrawState include:
All blend optimizations
Constant color/coverage stage optimizations

BUG=skia:
R=bsalomon@google.com, joshualitt@google.com

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/504203004
13 files changed