Reland add --use-more-webui runtime flag to toggle WebUI replacements for native dialogs.

chrome/browser/ui/webui/html_dialog_ui.h

 // Copyright (c) 2011 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_WEBUI_HTML_DIALOG_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_HTML_DIALOG_UI_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 82 matching lines @@
     // Height of the dialog.
     int height;
     // The JSON input to pass to the dialog when showing it.
     std::string json_input;
   };
 
   // When created, the property should already be set on the TabContents.
   explicit HtmlDialogUI(TabContents* tab_contents);
   virtual ~HtmlDialogUI();
 
+  // Close the dialog, passing the specified arguments to the close handler.
+  void CloseDialog(const base::ListValue* args);
+
   // Returns the PropertyBag accessor object used to write the delegate pointer
   // into the TabContents (see class-level comment above).
   static PropertyAccessor<HtmlDialogUIDelegate*>& GetPropertyAccessor();
 
  private:
   // WebUI
   virtual void RenderViewCreated(RenderViewHost* render_view_host) OVERRIDE;
 
   // JS message handler.
   void OnDialogClosed(const base::ListValue* args);
 
   DISALLOW_COPY_AND_ASSIGN(HtmlDialogUI);
 };
 
 // Displays external URL contents inside a modal HTML dialog.
 //
 // Intended to be the place to collect the settings and lockdowns
 // necessary for running external UI conponents securely (e.g., the
 // cloud print dialog).
 class ExternalHtmlDialogUI : public HtmlDialogUI {
  public:
   explicit ExternalHtmlDialogUI(TabContents* tab_contents);
   virtual ~ExternalHtmlDialogUI();
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_HTML_DIALOG_UI_H_