Const-ify DownloadStatusUpdaterDelegate methods.

content/browser/download/download_status_updater.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_STATUS_UPDATER_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_H_
 
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/weak_ptr.h"
 #include "content/common/content_export.h"
 
 class DownloadStatusUpdaterDelegate;
 
 // Keeps track of download progress for the entire browser.
 class CONTENT_EXPORT DownloadStatusUpdater
     : public base::SupportsWeakPtr<DownloadStatusUpdater> {
  public:
   DownloadStatusUpdater();
   ~DownloadStatusUpdater();
 
   void AddDelegate(DownloadStatusUpdaterDelegate* delegate);
   void RemoveDelegate(DownloadStatusUpdaterDelegate* delegate);
 
   // If the progress is known (i.e. we know the final size of all downloads),
   // returns true and puts a percentage (in range [0-1]) in |progress|. Also
   // returns the number of current downloads in |download_count|.
-  bool GetProgress(float* progress, int* download_count);
+  bool GetProgress(float* progress, int* download_count) const;
 
  private:
   // Returns the number of downloads that are in progress.
-  int64 GetInProgressDownloadCount();
+  int64 GetInProgressDownloadCount() const;
 
   typedef std::set<DownloadStatusUpdaterDelegate*> DelegateSet;
   DelegateSet delegates_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadStatusUpdater);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_H_