Add mip support to GrAHardwareBufferImageGenerator

Bug: skia:
Change-Id: I482d8f9937c86ed441016afef2d8f924282dd17a
Reviewed-on: https://skia-review.googlesource.com/63861
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
16 files changed