Created a DownloadManager interface, for use in unit tests..

content/browser/download/download_file_unittest.cc

 // 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.
 
 #include "base/file_util.h"
 #include "base/message_loop.h"
 #include "base/string_number_conversions.h"
 #include "content/browser/download/download_create_info.h"
 #include "content/browser/download/download_file.h"
 #include "content/browser/download/download_id.h"
@@ skipping 84 matching lines @@
     EXPECT_TRUE((*file)->in_progress());
     (*file)->AppendDataToFile(data.data(), data.size());
     expected_data_ += data;
     EXPECT_EQ(static_cast<int64>(expected_data_.size()),
               (*file)->bytes_so_far());
   }
 
  protected:
   DownloadStatusUpdater download_status_updater_;
   scoped_ptr<MockDownloadManagerDelegate> download_manager_delegate_;
-  scoped_refptr<DownloadManager> download_manager_;
+  scoped_refptr<DownloadManagerInterface> download_manager_;
 
   linked_ptr<net::FileStream> file_stream_;
 
   // DownloadFile instance we are testing.
   scoped_ptr<DownloadFile> download_file_;
 
  private:
   MessageLoop loop_;
   scoped_refptr<DownloadIdFactory> id_factory_;
   // UI thread.
@@ skipping 75 matching lines @@
   // Check the files.
   EXPECT_FALSE(file_util::PathExists(path_3));
   EXPECT_TRUE(file_util::PathExists(path_4));
 
   // Check the hash.
   EXPECT_TRUE(download_file_->GetSha256Hash(&hash));
   EXPECT_EQ(kDataHash, base::HexEncode(hash.data(), hash.size()));
 
   DestroyDownloadFile(&download_file_, 0);
 }