Support encrypted audio stream in demuxer.

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 988f224cf18e1ef05e4895fb48380aa04fb924eb..6748a28ed1563812077e5ebf2c8ace50a55988e7 100644
--- a/media/webm/webm_cluster_parser.h
+++ b/media/webm/webm_cluster_parser.h
@@ -22,6 +22,7 @@ class MEDIA_EXPORT WebMClusterParser : public WebMParserClient {
   WebMClusterParser(int64 timecode_scale,
                     int audio_track_num,
                     int video_track_num,
+                    const std::string& audio_encryption_key_id,
                     const std::string& video_encryption_key_id);
   virtual ~WebMClusterParser();
 
@@ -74,6 +75,7 @@ class MEDIA_EXPORT WebMClusterParser : public WebMParserClient {
 
   double timecode_multiplier_;  // Multiplier used to convert timecodes into
                                 // microseconds.
+  std::string audio_encryption_key_id_;
   std::string video_encryption_key_id_;
 
   WebMListParser parser_;