no need to refcnt colortables, since pixelrefs own them

BUG=skia:
R=halcanary@google.com, scroggo@google.com

Review URL: https://codereview.chromium.org/139463007

git-svn-id: http://skia.googlecode.com/svn/trunk@13098 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed