Add a const overload to DownloadItem::GetExternalData()

content/test/mock_download_item.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 CONTENT_TEST_MOCK_DOWNLOAD_ITEM_H_
 #define CONTENT_TEST_MOCK_DOWNLOAD_ITEM_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 98 matching lines @@
   MOCK_CONST_METHOD0(GetBrowserContext, content::BrowserContext*());
   MOCK_CONST_METHOD0(GetWebContents, content::WebContents*());
   MOCK_CONST_METHOD0(GetTargetFilePath, FilePath());
   MOCK_CONST_METHOD0(GetFileNameToReportUser, FilePath());
   MOCK_CONST_METHOD0(GetUserVerifiedFilePath, FilePath());
   MOCK_CONST_METHOD0(NeedsRename, bool());
   MOCK_METHOD1(OffThreadCancel, void(DownloadFileManager* file_manager));
   MOCK_CONST_METHOD1(DebugString, std::string(bool));
   MOCK_METHOD0(MockDownloadOpenForTesting, void());
   MOCK_METHOD1(GetExternalData, ExternalData*(const void*));
+  MOCK_CONST_METHOD1(GetExternalData, const ExternalData*(const void*));
   MOCK_METHOD2(SetExternalData, void(const void*, ExternalData*));
 };
 
 }  // namespace content
 
 #endif  // CONTENT_TEST_MOCK_DOWNLOAD_ITEM_H_