Add asAGradient shader extraction API.

Store initial gradient parameters.
Add compile asserts in GPU code for BitmapType ordering.

Review URL: http://codereview.appspot.com/4178063

git-svn-id: http://skia.googlecode.com/svn/trunk@845 2bbb7eff-a529-9590-31e7-b0007b416f81
5 files changed