Add support to communicate the frame visibility state to the browser.

This will allow the browser to be the source of freezing/resuming
individual iframes under certain situations.

BUG=907125

Change-Id: Ib1e3af74ba818c1532daec90266f12fc08306ef0
Reviewed-on: https://chromium-review.googlesource.com/c/1444213
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628132}
29 files changed