Remove (unused) GrBlend.cpp, and some GrColor helpers

Bug: skia:
Change-Id: I9a99cb28fd239371ca21b4a918e802606afe9da0
Reviewed-on: https://skia-review.googlesource.com/155840
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
4 files changed