Settings: Clear focus if overlay.focus() is not called.

Settings: Clear focus if overlay.focus() is not called.

Bugs:
* Open a setting overlay directly from ominibox (e.g. enter
  chrome://settings/fonts). The setting search box is still focused and we
  can enter text to it.
* Open do-not-track-confirm overlay or spelling-confirm overlay, switch to
  antoher tab, then switch back to the settings tab. "Learn More" link is
  focused unexpectedly.

Root cause:
A change to options_page.js [1] was incomplete. We should remove focus
anyway even if there are no keyboard-focused elements.

[1] http://src.chromium.org/viewvc/chrome/trunk/src/chrome/browser/resources/options/options_page.js?r1=214614&r2=214613&pathrev=214614

BUG=267400,268796

Review URL: https://chromiumcodereview.appspot.com/22342004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@216322 0039d316-1c4b-4281-b951-d872f2087c98