make RRect and Oval first-class drawing primitives in SkCanvas.
add RRect as a first-class clip primitive.
Review URL: https://codereview.appspot.com/6923058

git-svn-id: http://skia.googlecode.com/svn/trunk@6762 2bbb7eff-a529-9590-31e7-b0007b416f81
23 files changed