Revert "remove unused SkBitmap::copyPixelsTo"

This reverts commit 0f3fdfacf32261f943dcac5cdfd14475011f40db.

Reason for revert: Blink-headless in Google3 needs an update too.

Original change's description:
> remove unused SkBitmap::copyPixelsTo
> 
> Needs https://codereview.chromium.org/2812853002/ to land first
> 
> Bug: skia:6465
> Change-Id: I531e33b2848cd995f20844786ed1a8d34d63fb64
> Reviewed-on: https://skia-review.googlesource.com/13171
> Reviewed-by: Mike Reed <reed@google.com>
> Commit-Queue: Mike Reed <reed@google.com>
> 

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

Change-Id: I5e7c4b0d05772e4948cb1dffdcc40e095fbdba41
Reviewed-on: https://skia-review.googlesource.com/13185
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed