Revert "Revert "Add a flag to GrSurfaceFlags that requires the texture to be cleared upon creation. ""

This reverts commit a9e795eab5f59a52d96b8fdc39351452835f5eb9.

Bug: skia:
Change-Id: Ibfc51497ae99f332f8f72a799393a1b2996f7f3f
Reviewed-on: https://skia-review.googlesource.com/17767
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
14 files changed