Add an origin flag for backend (external) textures.  Some textures in WebKit have a topdown orientation, and skia needs to be notified of this, so that they are not drawn upside-down.

Review URL: https://codereview.appspot.com/7200048

git-svn-id: http://skia.googlecode.com/svn/trunk@7414 2bbb7eff-a529-9590-31e7-b0007b416f81
13 files changed