Fix clipping and stencil layer issues

bug:8235699

Ensure rectangle clipping operations disable deferring when necessary
(i.e., when the op might create a non-rect region), including in
DisplayList::setViewProperties

Additionally, makes clipping with a kUnion always use a region, for
consistency with software rendering

Change-Id: I6730f1a80250bcf3f91cd4afde646d470a12dbc2