Remove usage of kReturnToCache_FlagBit in C2D layer bridge.

BUG=skia:2889

Review URL: https://codereview.chromium.org/660083002

git-svn-id: svn://svn.chromium.org/blink/trunk@184191 bbb929c8-8fbe-4397-9dbb-9b2b20218538