Const-ify DownloadStatusUpdaterDelegate methods.

content/browser/download/download_status_updater_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_STATUS_UPDATER_DELEGATE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_DELEGATE_H_
 
 #include "base/basictypes.h"
 #include "content/common/content_export.h"
 
 class CONTENT_EXPORT DownloadStatusUpdaterDelegate {
  public:
   // Returns true if the progress is known (i.e. we know the final size
   // of all downloads).
-  virtual bool IsDownloadProgressKnown() = 0;
+  virtual bool IsDownloadProgressKnown() const = 0;
 
   // Returns the number of downloads that are in progress.
-  virtual int64 GetInProgressDownloadCount() = 0;
+  virtual int64 GetInProgressDownloadCount() const = 0;
 
   // Returns the amount of received data, in bytes.
-  virtual int64 GetReceivedDownloadBytes() = 0;
+  virtual int64 GetReceivedDownloadBytes() const = 0;
 
   // Returns the final size of all downloads, in bytes.
-  virtual int64 GetTotalDownloadBytes() = 0;
+  virtual int64 GetTotalDownloadBytes() const = 0;
 
  protected:
   virtual ~DownloadStatusUpdaterDelegate() {}
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATUS_UPDATER_DELEGATE_H_