Add flag on GrBackendTexture to say whether texture is mipped or not

Bug: skia:
Change-Id: Ia684e3daf779ec2feaaec64c04dabf5cb03cd07a
Reviewed-on: https://skia-review.googlesource.com/57821
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
31 files changed