MD Downloads: track downloads in C++, dispatch discrete JS updates

chrome/browser/ui/webui/md_downloads/md_downloads_ui.h

 // Copyright (c) 2012 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_MD_DOWNLOADS_MD_DOWNLOADS_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_MD_DOWNLOADS_MD_DOWNLOADS_UI_H_
 
 #include "base/macros.h"
 #include "content/public/browser/web_ui_controller.h"
 #include "ui/base/layout.h"
 
 namespace base {
 class RefCountedMemory;
 }
 
+namespace content {
+class RenderViewHost;
+}
+
+class MdDownloadsDOMHandler;
+
 class MdDownloadsUI : public content::WebUIController {
  public:
   explicit MdDownloadsUI(content::WebUI* web_ui);
 
   static base::RefCountedMemory* GetFaviconResourceBytes(
       ui::ScaleFactor scale_factor);
 
+  // content::WebUIController:
+  void RenderViewReused(content::RenderViewHost* render_view_host) override;
+
  private:
+  MdDownloadsDOMHandler* handler_;  // Weak.
+
   DISALLOW_COPY_AND_ASSIGN(MdDownloadsUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_MD_DOWNLOADS_MD_DOWNLOADS_UI_H_