Created an interface for DownloadFile, for use in unit tests.

content/browser/download/base_file.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_BASE_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_
 #pragma once
 
 #include <string>
 
 #include "base/file_path.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/browser/power_save_blocker.h"
 #include "content/common/content_export.h"
 #include "googleurl/src/gurl.h"
+#include "net/base/file_stream.h"
 #include "net/base/net_errors.h"
 
 namespace crypto {
 class SecureHash;
 }
 namespace net {
 class FileStream;
 }
 
 // File being downloaded and saved to disk. This is a base class
@@ skipping 46 matching lines @@
   virtual void CreateFileStream();  // For testing.
   // Returns net::OK on success, or a network error code on failure.
   net::Error Open();
   void Close();
 
   // Full path to the file including the file name.
   FilePath full_path_;
 
  private:
   friend class BaseFileTest;
-  friend class DownloadFileWithMockStream;
 
   static const size_t kSha256HashLen = 32;
 
   // Source URL for the file being downloaded.
   GURL source_url_;
 
   // The URL where the download was initiated.
   GURL referrer_url_;
 
   // OS file stream for writing
@@ skipping 15 matching lines @@
   unsigned char sha256_hash_[kSha256HashLen];
 
   // Indicates that this class no longer owns the associated file, and so
   // won't delete it on destruction.
   bool detached_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseFile);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_