Support interstitials with no primary button

components/security_interstitials/core/controller_client.h

Index: components/security_interstitials/core/controller_client.h
diff --git a/components/security_interstitials/core/controller_client.h b/components/security_interstitials/core/controller_client.h
index 33d9cece49438ed842586b792cf8a538509ad5f8..6c2a8ce9188dfd9be6f6c66849812201395fb8be 100644
--- a/components/security_interstitials/core/controller_client.h
+++ b/components/security_interstitials/core/controller_client.h
@@ -91,6 +91,9 @@ class ControllerClient {
 
   virtual const std::string& GetApplicationLocale() const = 0;
 
+  // Whether it is possible to go 'Back to safety'. Specifially for WebViews.
+  virtual bool CanGoBack() = 0;
+
  protected:
   virtual const std::string GetExtendedReportingPrefName() const = 0;