Implement OOPIF double-tap-zoom.

This CL adds the required pathways to support double-tap-zoom for OOPIF.

1) Modifies WebFrameWidgetImpl to get the box_bounds of the double-
   tapped element, and
2) sends the tapped point and box_bounds to the browser, where
3) RenderFrameHostImpl transforms them into root-view coordinates, and
4) sends them to the renderer via the main-frame's RenderViewHostImpl.
5) From there RenderViewImpl invokes WebViewImpl's
   AnimateDoubleTapZoom.

Bug: 734209
Change-Id: Ic55afb6154356d676872ced93f64a243190cf289
Reviewed-on: https://chromium-review.googlesource.com/c/1298081
Reviewed-by: Daniel Cheng <[email protected]>
Reviewed-by: Ken Buchanan <[email protected]>
Reviewed-by: David Bokan <[email protected]>
Commit-Queue: James MacLean <[email protected]>
Cr-Commit-Position: refs/heads/master@{#612371}
17 files changed