Add missing macros includes in media/.

media/formats/webm/webm_content_encodings.h

 // Copyright 2014 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 MEDIA_FORMATS_WEBM_WEBM_CONTENT_ENCODINGS_H_
 #define MEDIA_FORMATS_WEBM_WEBM_CONTENT_ENCODINGS_H_
 
 #include <string>
 
+#include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 class MEDIA_EXPORT ContentEncoding {
  public:
   // The following enum definitions are based on the ContentEncoding element
   // specified in the Matroska spec.
 
@@ skipping 58 matching lines @@
   EncryptionAlgo encryption_algo_;
   std::string encryption_key_id_;
   CipherMode cipher_mode_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentEncoding);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FORMATS_WEBM_WEBM_CONTENT_ENCODINGS_H_