Revert "Revert "Plumb the use of GrBackendRenderTarget throughout Skia""

Revert "Revert "Plumb the use of GrBackendRenderTarget throughout Skia""

This reverts commit e3bd422fafc74dd3410c3de24a576635be92c3b4.

Reason for revert: Pre-req changes have all landed in other projects at this point.

Original change's description:
> 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>
>

TBR=egdaniel@google.com,bsalomon@google.com,robertphillips@google.com,reviews@skia.org
# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ib7ab94aada8a7cb80fe38f24daf32f9208c5b169
Reviewed-on: https://skia-review.googlesource.com/14826
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>