Revert of remove unused SkCachingPixelRef (patchset #1 id:1 of https://codereview.chromium.org/1364743002/ )

Reason for revert:
Build failure: https://uberchromegw.corp.google.com/i/client.skia.compile/builders/Build-Ubuntu-GCC-Arm7-Debug-Android_FrameworkDefs/builds/1146

Original issue's description:
> remove unused SkCachingPixelRef
>
> BUG=skia:
> TBR=
>
> Committed: https://skia.googlesource.com/skia/+/70d58b7da535e32bcac35739d11ab8367e99f224

TBR=halcanary@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1359393004
4 files changed