Add attribute event listeners to visualViewport

These were previously available but removed in r407955. In the mean time
they made their way into the visualViewport draft spec:

https://wicg.github.io/ViewportAPI/spec.html#dom-visualviewport-onresize

But we forgot to actually re-add them. This patch adds them back in.

Bug: 760916
Change-Id: Ib2dc3dbd21d648d9118bbb88e61bba7b65369688
Reviewed-on: https://chromium-review.googlesource.com/658318
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501855}
13 files changed