Separate texture creation from uploading in GrGpu subclasses.

GrGpu base class still allows creation with initial data, but separated
at subclass level into create and then write pixels.

GrGpu handles determining which levels need clearing and GrGpu
subclasses take a mask and clear levels with mask bit set.

GrGLGpu uses three pronged clear strategy:
glClearTexImage() if supported, glClear() if format is FBO bindable, and
lastly glTexSubImage2D with zero'ed buffer.

Change-Id: I65fb1e60eed8f9d0896d686d3baeb10b57ff8f39
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/236676
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
21 files changed