When receiving an extension message that is accompanied by a user gesture, also allow window.focus to function.

BUG=325014

Review URL: https://codereview.chromium.org/98073004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242370 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242370