GitLab

This adds a second JavaScript API entry point to the Contextual Search
Overlay Panel that can be called from the panel content.

The new API allows changing the Overlay position from one open state
to another, or to close it, but not to open it.

BUG=834864

Change-Id: I4fe222edfcf030cfb086ddbb3ecec5071b5448f4
Reviewed-on: https://chromium-review.googlesource.com/1045178Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578189}