Revert "Replace SkSpecialImage::makeTightSubset with asImage"

This reverts commit 5df6db15dc04ea7f8c8fa7a7b58ecb881d7a70fe.

Reason for revert: Possibly blocking Chrome DEPS roll

Original change's description:
> Replace SkSpecialImage::makeTightSubset with asImage
> 
> This should allow the relanding of:
> 
> https://skia-review.googlesource.com/c/8450/ (Remove asTextureRef from SkSpecialImage & update effects accordingly (take 2))
> 
> Change-Id: I517af11036e3f44a280bbe6b9275f6c38f4a86a4
> Reviewed-on: https://skia-review.googlesource.com/8498
> 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: Ib5bebda78b2323e65a73504a61af918872ad231f
Reviewed-on: https://skia-review.googlesource.com/8607
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
6 files changed