webrtc-internals: rename mediadescriptor label

Renames the MediaStream "label" used e.g. in addStream and
onaddstream to "id" to be more aligned with the specification.

BUG=none

Review-Url: https://codereview.chromium.org/2495983002
Cr-Commit-Position: refs/heads/master@{#437863}

AUTHORS

@@ -539,6 +539,7 @@ Peter Collingbourne <peter@pcc.me.uk>
 Peter Gal <pgal.u-szeged@partner.samsung.com>
 Peter Molnar <pmolnar.u-szeged@partner.samsung.com>
 Philipp Hancke <fippo@andyet.net>
+Philipp Hancke <philipp.hancke@googlemail.com>
 Philippe Beauchamp <philippe.beauchamp@gmail.com>
 Philippe Beaudoin <philippe.beaudoin@gmail.com>
 Pierre-Antoine LaFayette <pierre.lafayette@gmail.com>

content/renderer/media/peer_connection_tracker.cc

@@ -90,8 +90,8 @@ static std::string SerializeMediaStreamComponent(
 
 static std::string SerializeMediaDescriptor(
     const blink::WebMediaStream& stream) {
-  std::string label = base::UTF16ToUTF8(base::StringPiece16(stream.id()));
-  std::string result = "label: " + label;
+  std::string id = base::UTF16ToUTF8(base::StringPiece16(stream.id()));
+  std::string result = "id: " + id;
   blink::WebVector<blink::WebMediaStreamTrack> tracks;
   stream.audioTracks(tracks);
   if (!tracks.isEmpty()) {