Add new UMA stats to get a handle on Downloads UI Usage

content/browser/download/download_manager_delegate.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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_DELEGATE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_DELEGATE_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 87 matching lines @@
 
   // Asks the user for the path to save a page. The delegate calls
   // SavePackage::OnPathPicked to give the answer.
   virtual void ChooseSavePath(const base::WeakPtr<SavePackage>& save_package,
                               const FilePath& suggested_path,
                               bool can_save_as_complete) = 0;
 
   // Informs the delegate that the progress of downloads has changed.
   virtual void DownloadProgressUpdated() = 0;
 
+  virtual void MarkDownloadOpened(int64 db_handle) = 0;
+
  protected:
   DownloadManagerDelegate() {}
 
   DISALLOW_COPY_AND_ASSIGN(DownloadManagerDelegate);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_MANAGER_DELEGATE_H_