Revert of Use SkBitmapCache to optimize readPixels on a texture-backed bitmap

Revert of Use SkBitmapCache to optimize readPixels on a texture-backed bitmap (patchset #6 id:100001 of https://codereview.chromium.org/533323002/)

Reason for revert:
Component inversions in Blink's printing/webgl-repeated-printing.html: https://storage.googleapis.com/chromium-layout-test-archives/linux_blink_rel/24033/layout-test-results/printing/webgl-repeated-printing-diff.txt

Reverting to unblock rolls.

Original issue's description:
> Use SkBitmapCache to optimize readPixels on a texture-backed bitmap
> 
> BUG=skia:2786
> 
> Committed: https://skia.googlesource.com/skia/+/95fd68e5ccd242a91e6dd827dd695f18661efbe6

TBR=junov@chromium.org,reed@google.com,bsalomon@google.com,piotaixr@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=skia:2786
Committed: https://skia.googlesource.com/skia/+/90dc6412b46fa0bcf01ce45feeb4934fb774e7eb

[f(malita), 2014-09-09 15:11:48]

Created Revert of Use SkBitmapCache to optimize readPixels on a texture-backed
bitmap

[commit-bot: I haz the power, 2014-09-09 15:12:43]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/fmalita@chromium.org/551523003/1

[commit-bot: I haz the power, 2014-09-09 15:12:49]

Committed patchset #1 (id:1) as 90dc6412b46fa0bcf01ce45feeb4934fb774e7eb