this has the changes Brian suggested git-svn-id: http://skia.googlecode.com/svn/trunk@8812 2bbb7eff-a529-9590-31e7-b0007b416f81
add inverse fill, reverse diff, and gm tests cleaned up some interfaces Review URL: https://codereview.chromium.org/14371011 git-svn-id: http://skia.googlecode.com/svn/trunk@8798 2bbb7eff-a529-9590-31e7-b0007b416f81