GitLab

Implement CloseContents for ExtensionOptionsGuest. CloseContents
propagates a 'close' event up to the <extensionoptions> node.
In WebUI, when the extension options overlay receives this event,
it will close the overlay.

Extension options pages that used window.close() to close their
tab in the old options page UI will now close their embedder
overlay.

BUG=386842, 386838

Review URL: https://codereview.chromium.org/490783002

Cr-Commit-Position: refs/heads/master@{#291554}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291554 0039d316-1c4b-4281-b951-d872f2087c98