Code: static Frame* ReuseExistingWindow(LocalFrame& active_frame,
                                  LocalFrame& lookup_frame,
                                  const AtomicString& frame_name,
                                  NavigationPolicy policy,
                                  const KURL& destination_url) {
  if (!frame_name.IsEmpty() && !EqualIgnoringASCIICase(frame_name, "_blank") &&
      policy == kNavigationPolicyIgnore) {
    if (Frame* frame = lookup_frame.FindFrameForNavigation(
            frame_name, active_frame, destination_url)) {
      if (!EqualIgnoringASCIICase(frame_name, "_self")) {
        if (Page* page = frame->GetPage()) {
           if (page == active_frame.GetPage())
             page->GetFocusController().SetFocusedFrame(frame);
           else
            page->GetChromeClient().Focus();
         }
       }
       return frame;
    }
  }
  return nullptr;
}

Vulnerability Type: 
CWE ID: 
Summary: A JavaScript focused window could overlap the fullscreen notification in Fullscreen in Google Chrome prior to 66.0.3359.117 allowed a remote attacker to obscure the full screen warning via a crafted HTML page.
Commit Message: If a page calls |window.focus()|, kick it out of fullscreen.

BUG=776418, 800056

Change-Id: I1880fe600e4814c073f247c43b1c1ac80c8fc017
Reviewed-on: https://chromium-review.googlesource.com/852378
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533790}