Support interstitials with no primary button

components/security_interstitials/core/controller_client.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_SECURITY_INTERSTITIALS_CORE_CONTROLLER_CLIENT_H_
 #define COMPONENTS_SECURITY_INTERSTITIALS_CORE_CONTROLLER_CLIENT_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 53 matching lines @@
   void OpenExtendedReportingPrivacyPolicy();
   void OpenExtendedReportingWhitepaper();
 
   // If available, open the operating system's date/time settings.
   virtual bool CanLaunchDateAndTimeSettings() = 0;
   virtual void LaunchDateAndTimeSettings() = 0;
 
   // Close the error and go back to the previous page. This applies to
   // situations where navigation is blocked before committing.
   virtual void GoBack() = 0;
+  // Whether it is possible to go 'Back to safety'.
+  virtual bool CanGoBack() = 0;
 
   // 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.
   virtual void GoBackAfterNavigationCommitted() = 0;
 
   // Close the error and proceed to the blocked page.
   virtual void Proceed() = 0;
 
   // Reload the blocked page to see if it succeeds now.
@@ skipping 12 matching lines @@
 
  private:
   std::unique_ptr<MetricsHelper> metrics_helper_;
 
   DISALLOW_COPY_AND_ASSIGN(ControllerClient);
 };
 
 }  // namespace security_interstitials
 
 #endif  // COMPONENTS_SECURITY_INTERSTITIALS_CORE_CONTROLLER_CLIENT_H_