Return correctly mapped bounds from GrOvalRenderer.

Return correctly mapped bounds from GrOvalRenderer.

Before we were returning non transformed bounds for the ovals instead of
device bounds from the various draw calls. This was causing us to do dst
copies from the wrong portion of the screen when there was some transform
on the matrix.

This fixes the gpu issues from the new imagefilters-xfermodes gm as well an
old bug from the srcmode GM.

BUG=skia:

Review URL: https://codereview.chromium.org/1090453003