Generate and assign media track ids in demuxers.

media/blink/webmediaplayer_impl_unittest.cc

Index: media/blink/webmediaplayer_impl_unittest.cc
diff --git a/media/blink/webmediaplayer_impl_unittest.cc b/media/blink/webmediaplayer_impl_unittest.cc
index 1b345e4d584294e677f19759f1c432cb0114e67e..3a94a9af25eac7eeb9a5a2fed33c3505fa3b306f 100644
--- a/media/blink/webmediaplayer_impl_unittest.cc
+++ b/media/blink/webmediaplayer_impl_unittest.cc
@@ -56,7 +56,7 @@ class DummyWebMediaPlayerClient : public blink::WebMediaPlayerClient {
       const blink::WebString& label,
       const blink::WebString& language,
       bool enabled) override {
-    return 0;
+    return blink::WebMediaPlayer::TrackId();
   }
   void removeAudioTrack(blink::WebMediaPlayer::TrackId) override {}
   blink::WebMediaPlayer::TrackId addVideoTrack(
@@ -65,7 +65,7 @@ class DummyWebMediaPlayerClient : public blink::WebMediaPlayerClient {
       const blink::WebString& label,
       const blink::WebString& language,
       bool selected) override {
-    return 0;
+    return blink::WebMediaPlayer::TrackId();
   }
   void removeVideoTrack(blink::WebMediaPlayer::TrackId) override {}
   void addTextTrack(blink::WebInbandTextTrack*) override {}