Support interstitials with no primary button

components/security_interstitials/content/security_interstitial_controller_client.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/security_interstitials/content/security_interstitial_controller_client.h"
 
 #include <utility>
 
 #include "components/prefs/pref_service.h"
 #include "components/safe_browsing_db/safe_browsing_prefs.h"
@@ skipping 28 matching lines @@
 
 content::InterstitialPage*
 SecurityInterstitialControllerClient::interstitial_page() {
   return interstitial_page_;
 }
 
 void SecurityInterstitialControllerClient::GoBack() {
   interstitial_page_->DontProceed();
 }
 
+bool SecurityInterstitialControllerClient::CanGoBack() {
+  return web_contents_->GetController().CanGoBack();
+}
+
 void SecurityInterstitialControllerClient::GoBackAfterNavigationCommitted() {
   // If the offending entry has committed, go back or to a safe page without
   // closing the error page. This error page will be closed when the new page
   // commits.
   if (web_contents_->GetController().CanGoBack()) {
     web_contents_->GetController().GoBack();
   } else {
     web_contents_->GetController().LoadURL(
         default_safe_page_, content::Referrer(),
         ui::PAGE_TRANSITION_AUTO_TOPLEVEL, std::string());
@@ skipping 34 matching lines @@
 bool SecurityInterstitialControllerClient::CanLaunchDateAndTimeSettings() {
   NOTREACHED();
   return false;
 }
 
 void SecurityInterstitialControllerClient::LaunchDateAndTimeSettings() {
   NOTREACHED();
 }
 
 }  // namespace security_interstitials