Early out of empty invalidations.

We currently early out in RenderView::repaintViewRectangle if the invalidation
isEmpty(). This CL adds a similar early out to
RenderObject::repaintUsingContainer(). While these invalidations will be
filtered at the RenderView level there is a bunch of logic between those two
places that can be skipped.

This also cleans up the trace events which are output as we will no-longer see
events for invalidations that will be filtered later for being empty.

Review URL: https://codereview.chromium.org/247823002

git-svn-id: svn://svn.chromium.org/blink/trunk@172380 bbb929c8-8fbe-4397-9dbb-9b2b20218538