extend fastbounds impls to include maskfilters and drawloopers. This allows

extend fastbounds impls to include maskfilters and drawloopers. This allows
us to perform quick-rejects when drawing objects with shadows (esp. text).
WebKit draws shadows w/ a looper (fg and shadow) and a maskfilter on the
shadow layer.

git-svn-id: http://skia.googlecode.com/svn/trunk@3103 2bbb7eff-a529-9590-31e7-b0007b416f81