Code:  void WebContentsImpl::FocusThroughTabTraversal(bool reverse) {
   if (ShowingInterstitialPage()) {
    GetRenderManager()->interstitial_page()->FocusThroughTabTraversal(reverse);
     return;
   }
   RenderWidgetHostView* const fullscreen_view =
      GetFullscreenRenderWidgetHostView();
  if (fullscreen_view) {
    fullscreen_view->Focus();
    return;
  }
  GetRenderViewHost()->SetInitialFocus(reverse);
 }

Vulnerability Type: 
CWE ID: CWE-20
Summary: Inappropriate implementation in interstitials in Google Chrome prior to 60.0.3112.78 for Mac allowed a remote attacker to spoof the contents of the omnibox via a crafted HTML page.
Commit Message: Don't show current RenderWidgetHostView while interstitial is showing.

Also moves interstitial page tracking from RenderFrameHostManager to
WebContents, since interstitial pages are not frame-specific. This was
necessary for subframes to detect if an interstitial page is showing.

BUG=729105
TEST=See comment 13 of bug for repro steps
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2938313002
Cr-Commit-Position: refs/heads/master@{#480117}