Move MockFFmpeg instance setting into the constructor/destructor.

media/base/mock_ffmpeg.h

Index: media/base/mock_ffmpeg.h
===================================================================
--- media/base/mock_ffmpeg.h	(revision 75179)
+++ media/base/mock_ffmpeg.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -65,10 +65,6 @@
   // Used for verifying check points during tests.
   MOCK_METHOD1(CheckPoint, void(int id));
 
-  // Setter/getter for the global instance of MockFFmpeg.
-  static void set(MockFFmpeg* instance);
-  static MockFFmpeg* get();
-
   // Returns the URLProtocol registered by the FFmpegGlue singleton.
   static URLProtocol* protocol();
 
@@ -80,7 +76,6 @@
   void dec_outstanding_packets();
 
  private:
-  static MockFFmpeg* instance_;
   static URLProtocol* protocol_;
 
   // Tracks the number of packets allocated by calls to av_read_frame() and