Revert "Remove asTextureRef from SkSpecialImage & update effects accordingly"

Revert "Remove asTextureRef from SkSpecialImage & update effects accordingly"

This reverts commit e88cf6b7aa5deaeaa9dab18ada7d9d11e1e4be12.

Reason for revert: See if breaking DEPS roll

Original change's description:
> Remove asTextureRef from SkSpecialImage & update effects accordingly
>
> This CL also renames SkSpecialImage::asTextureProxy to asTextureProxyRef
>
> Change-Id: I5ed8e475bb9688453b825ae4500ed0e8d324b5ac
> Reviewed-on: https://skia-review.googlesource.com/7995
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Robert Phillips <robertphillips@google.com>
>

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

Change-Id: I227cbd5fcaf7e2f86e858331d9ec7ff7a5f203ca
Reviewed-on: https://skia-review.googlesource.com/8184
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>