Mountain Lion: use the system download progress.

chrome/browser/download/download_status_updater.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_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_H_
 
 #include <set>
 
 #include "base/basictypes.h"
@@ skipping 24 matching lines @@
   // Methods inherited from content::DownloadManager::Observer.
   virtual void ModelChanged(content::DownloadManager* manager) OVERRIDE;
   virtual void ManagerGoingDown(content::DownloadManager* manager) OVERRIDE;
 
   // Methods inherited from content::DownloadItem::Observer.
   virtual void OnDownloadUpdated(content::DownloadItem* download) OVERRIDE;
   virtual void OnDownloadOpened(content::DownloadItem* download) OVERRIDE;
   virtual void OnDownloadDestroyed(content::DownloadItem* download) OVERRIDE;
 
  protected:
-  // Update the app icon. Virtual to be overridable for testing.
-  virtual void UpdateAppIconDownloadProgress();
+  // Platform-specific function to update the platform UI for download progress.
+  // |download| is the download item that changed. Implementations should not
+  // hold the value of |download| as it is not guaranteed to remain valid.
+  // Virtual to be overridable for testing.
+  virtual void UpdateAppIconDownloadProgress(content::DownloadItem* download);
 
  private:
-  // Update the internal state tracking an item.
-  void UpdateItem(content::DownloadItem* download);
+  // Update the internal state tracking an item. Returns true if the item was
+  // added to the set of tracked items.
+  bool UpdateItem(content::DownloadItem* download);
 
   std::set<content::DownloadManager*> managers_;
   std::set<content::DownloadItem*> items_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadStatusUpdater);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_H_