Fix repainting of composited RenderViews

Blink r175423 fixed non-composited nested RenderView repainting
for repaint-after-layout, but in the process broke repainting of
composited nested RenderViews for all code paths. The fix is to
correctly issue repaints to the backing store of composited
RenderViews regardless of whether they're nested.

BUG=381022
R=esprehn@chromium.org

Review URL: https://codereview.chromium.org/318183002

git-svn-id: svn://svn.chromium.org/blink/trunk@175718 bbb929c8-8fbe-4397-9dbb-9b2b20218538