Revert "Plumb GrBackendTexture throughout skia."

Revert "Plumb GrBackendTexture throughout skia."

This reverts commit 7da62b9059f3c1d31624a0e4da96ee5f908f9c12.

Reason for revert: fix android roll

Original change's description:
> Plumb GrBackendTexture throughout skia.
>
> Bug: skia:
> Change-Id: I1bae6768ee7229818a83ba608035a1f7867e6875
> Reviewed-on: https://skia-review.googlesource.com/13645
> Commit-Queue: Greg Daniel <egdaniel@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
>

TBR=egdaniel@google.com,bsalomon@google.com,robertphillips@google.com,brianosman@google.com,reviews@skia.org,stani@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I5cb8763cc837c83ebc6d10366fe2dd3efe35fb89
Reviewed-on: https://skia-review.googlesource.com/13773
Reviewed-by: Stan Iliev <stani@google.com>
Commit-Queue: Stan Iliev <stani@google.com>