Switch over to using the SkImageFilter::CropRect API for filter primitive subregion in Blink.

BUG=229910
R=schenney@chromium.org

Review URL: https://codereview.chromium.org/27063002

git-svn-id: svn://svn.chromium.org/blink/trunk@159692 bbb929c8-8fbe-4397-9dbb-9b2b20218538