Allow navigation while a JavaScript dialog is up.

chrome/browser/ui/javascript_dialogs/javascript_dialog_tab_helper.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_JAVASCRIPT_DIALOGS_JAVASCRIPT_DIALOG_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_JAVASCRIPT_DIALOGS_JAVASCRIPT_DIALOG_TAB_HELPER_H_
 
 #include <memory>
 
 #include "base/callback_forward.h"
@@ skipping 42 matching lines @@
                              const DialogClosedCallback& callback) override;
   bool HandleJavaScriptDialog(content::WebContents* web_contents,
                               bool accept,
                               const base::string16* prompt_override) override;
   void CancelDialogs(content::WebContents* web_contents,
                      bool suppress_callbacks,
                      bool reset_state) override;
 
   // WebContentsObserver:
   void WasHidden() override;
+  void DidStartNavigation(
+      content::NavigationHandle* navigation_handle) override;
+  void DidStartNavigationToPendingEntry(
+      const GURL& url,
+      content::ReloadType reload_type) override;
 
   // BrowserListObserver:
   void OnBrowserSetLastActive(Browser* browser) override;
 
  private:
   friend class content::WebContentsUserData<JavaScriptDialogTabHelper>;
   enum class DismissalCause;
 
   void LogDialogDismissalCause(DismissalCause cause);
 
@@ skipping 21 matching lines @@
   // itself calls it, but in the cases where the dialog is closed not by the
   // user's input but by a call to |CloseDialog|, this class will call it.
   content::JavaScriptDialogManager::DialogClosedCallback dialog_callback_;
 
   base::Closure dialog_shown_;
 
   DISALLOW_COPY_AND_ASSIGN(JavaScriptDialogTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_JAVASCRIPT_DIALOGS_JAVASCRIPT_DIALOG_TAB_HELPER_H_