Revert "Plumb the use of GrBackendRenderTarget throughout Skia"

This reverts commit fdd77daedbba3b7c53be74a82fb9fae891b51696.

Reason for revert: Apparently I have a few more build files to update before this can land.

Original change's description:
> Plumb the use of GrBackendRenderTarget throughout Skia
> 
> Bug: skia:
> Change-Id: Ib99a58d9552f5c7b8d77c09dcc72fa88326c26aa
> Reviewed-on: https://skia-review.googlesource.com/14148
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>
> 

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

Change-Id: I984e1909870182474c4c3cce257f01b6a9d8581f
Reviewed-on: https://skia-review.googlesource.com/14531
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
22 files changed