Add support for encrypted WebM files as defined in the RFC.

media/webm/webm_cluster_parser.h

Index: media/webm/webm_cluster_parser.h
diff --git a/media/webm/webm_cluster_parser.h b/media/webm/webm_cluster_parser.h
index ea76d30370f9f13e37e19e23cdbfcdb9b98ea108..0deb84a1ab66bc169592e9819003117141747c59 100644
--- a/media/webm/webm_cluster_parser.h
+++ b/media/webm/webm_cluster_parser.h
@@ -19,6 +19,11 @@ class MEDIA_EXPORT WebMClusterParser : public WebMParserClient {
  public:
   typedef std::deque<scoped_refptr<StreamParserBuffer> > BufferQueue;
 
+  // Sizes are defined by the WebM encryption specification.
+  // http://wiki.webmproject.org/encryption/webm-encryption-rfc
+  static const int kDecryptionKeySize = 16;
+  static const int kIvSize = 8;
+
   WebMClusterParser(int64 timecode_scale,
                     int audio_track_num,
                     int video_track_num,