This revealed that the displacement map was not handling clipping or upstream cropping at all well (the color would "swim" through the displacement at the edge of the clip rect). Fixed by passing through the correct offsets to the bitmap accesses in both raster and GPU paths. Same for morphology.
R=sugoi@google.com
Review URL: https://codereview.chromium.org/137053003
git-svn-id: http://skia.googlecode.com/svn/trunk@13127 2bbb7eff-a529-9590-31e7-b0007b416f81