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

content/browser/download/download_id_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 "content/browser/download/download_id.h"
 
 #include <algorithm>
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 26 matching lines @@
     }
   }
 
   ~DownloadIdTest() {
     for (size_t i = 0; i < num_managers_; ++i)
       download_managers_[i] = NULL;  // Releases & deletes.
   }
 
  protected:
   scoped_ptr<MockDownloadManagerDelegate> download_manager_delegate_;
-  scoped_refptr<DownloadManager> download_managers_[2];
+  scoped_refptr<DownloadManagerInterface> download_managers_[2];
   MessageLoopForUI message_loop_;
   // Necessary to delete |DownloadManager|s.
   content::TestBrowserThread ui_thread_;
   size_t num_managers_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadIdTest);
 };
 
 TEST_F(DownloadIdTest, Local) {
   DownloadId id1(download_managers_[0], 23);
@@ skipping 84 matching lines @@
   EXPECT_EQ(kLocalId[2], map[id3]);
   last = map.end();
   EXPECT_FALSE(last == map.find(id1));
   EXPECT_FALSE(last == map.find(id2));
   EXPECT_FALSE(last == map.find(id3));
 
   EXPECT_FALSE(id1 == id2);
   EXPECT_LT(id1, id2);
 }