Remove FrameView::DeferredRepaintScope

Our compositor knows how to do unions and deal with repaints for us, we
don't need to be deferring the repaints until after recalc style or
layout like this code was trying to do.

R=jamesr@chromium.org,eseidel@chromium.org

Review URL: https://codereview.chromium.org/134643008

git-svn-id: svn://svn.chromium.org/blink/trunk@165130 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add blink::WebWaitableEvent interface (blink side)

chromium side: https://codereview.chromium.org/133493003/

BUG=334263

Review URL: https://codereview.chromium.org/138303002

git-svn-id: svn://svn.chromium.org/blink/trunk@165131 bbb929c8-8fbe-4397-9dbb-9b2b20218538