Support encrypted audio stream in demuxer.

media/webm/webm_tracks_parser.cc

Index: media/webm/webm_tracks_parser.cc
diff --git a/media/webm/webm_tracks_parser.cc b/media/webm/webm_tracks_parser.cc
index bf039bf77bde53870e56cc3d0564cebde0c74762..dcc3331d44988d7d2061a42b2fee1536c61499d6 100644
--- a/media/webm/webm_tracks_parser.cc
+++ b/media/webm/webm_tracks_parser.cc
@@ -25,15 +25,6 @@ WebMTracksParser::WebMTracksParser()
 
 WebMTracksParser::~WebMTracksParser() {}
 
-const std::string& WebMTracksParser::video_encryption_key_id() const {
-  if (!video_content_encodings_client_.get())
-    return EmptyString();
-
-  DCHECK(!video_content_encodings_client_->content_encodings().empty());
-  return video_content_encodings_client_->content_encodings()[0]->
-      encryption_key_id();
-}
-
 int WebMTracksParser::Parse(const uint8* buf, int size) {
   track_type_ =-1;
   track_num_ = -1;
@@ -50,7 +41,6 @@ int WebMTracksParser::Parse(const uint8* buf, int size) {
   return parser.IsParsingComplete() ? result : 0;
 }
 
-
 WebMParserClient* WebMTracksParser::OnListStart(int id) {
   if (id == kWebMIdContentEncodings) {
     DCHECK(!track_content_encodings_client_.get());
@@ -84,14 +74,16 @@ bool WebMTracksParser::OnListEnd(int id) {
     if (track_type_ == kWebMTrackTypeVideo) {

[ddorwin, 2012/10/11 05:18:22]

Strange that video is processed first here. It seems to be the opposite order
most places and in the header file.

[xhwang, 2012/10/11 16:36:10]

Done.

       video_track_num_ = track_num_;
       if (track_content_encodings_client_.get()) {
-        video_content_encodings_client_ =
-            track_content_encodings_client_.Pass();
+        DCHECK(!track_content_encodings_client_->content_encodings().empty());
+        video_encryption_key_id_ = track_content_encodings_client_->
+            content_encodings()[0]->encryption_key_id();

[ddorwin, 2012/10/11 05:18:22]

Why is it the first encoding? Maybe we should comment this.
I'm guessing because we only support one type of encoding. Is there a way to
DCHECK the type of the encoding?

[xhwang, 2012/10/11 16:36:10]

Added more comments and more checks. fgalligan@: please double check if this is
correct as per WebM encryption RFC.

       }
     } else if (track_type_ == kWebMTrackTypeAudio) {
       audio_track_num_ = track_num_;
       if (track_content_encodings_client_.get()) {
-        audio_content_encodings_client_ =
-            track_content_encodings_client_.Pass();
+        DCHECK(!track_content_encodings_client_->content_encodings().empty());
+        audio_encryption_key_id_ = track_content_encodings_client_->
+            content_encodings()[0]->encryption_key_id();
       }
     } else {
       DVLOG(1) << "Unexpected TrackType " << track_type_;