Fixed the crash when adding a chromium sink to remote audio track or

Fixed the crash when adding a chromium sink to remote audio track or adding a track to peerconnection more than once.

NOTRY=true

BUG=396447
TEST=open peerConnection demo, http://googlechrome.github.io/webrtc/samples/web/content/peerconnection/
2. start a call
3. Open JS console and input below codes:
# adding a chromium sink to remote audio track:
var v = new webkitMediaStream();
v.addTrack(pc2.getRemoteStreams()[0].getAudioTracks()[0]);
var a = document.createElement('audio');
a.src = URL.createObjectURL(v);

# add a track to peer connection more than once:
var v = new webkitMediaStream();
v.addTrack(pc2.getRemoteStreams()[0].getAudioTracks()[0]);
pc1.addStream(v);

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=285528

[no longer working on chromium, 2014-07-23 13:57:39]

Ronghua, could you please review this CL?
I might write some browser test in another CL since I don't want to merge the
the test to previous MLs.

[Ronghua Wu (Left Chromium), 2014-07-23 15:53:43]

https://codereview.chromium.org/411903002/diff/1/content/browser/renderer_hos...
File content/browser/renderer_host/media/media_stream_track_metrics_host.cc
(right):

https://codereview.chromium.org/411903002/diff/1/content/browser/renderer_hos...
content/browser/renderer_host/media/media_stream_track_metrics_host.cc:59: void
MediaStreamTrackMetricsHost::OnRemoveTrack(uint64 id) {
curious, when will OnAddTrack and OnRemoveTrack be called?

https://codereview.chromium.org/411903002/diff/1/content/public/renderer/medi...
File content/public/renderer/media_stream_audio_sink.cc (right):

https://codereview.chromium.org/411903002/diff/1/content/public/renderer/medi...
content/public/renderer/media_stream_audio_sink.cc:22: LOG(ERROR) << "Only local
audio track is supported now";
add info about what is "supported".

E.g. Can't add a remote track to a local stream.

https://codereview.chromium.org/411903002/diff/1/content/public/renderer/medi...
content/public/renderer/media_stream_audio_sink.cc:37: LOG(ERROR) << "Only local
audio track is supported now";
dito

[no longer working on chromium, 2014-07-24 13:23:31]

https://codereview.chromium.org/411903002/diff/1/content/browser/renderer_hos...
File content/browser/renderer_host/media/media_stream_track_metrics_host.cc
(right):

https://codereview.chromium.org/411903002/diff/1/content/browser/renderer_hos...
content/browser/renderer_host/media/media_stream_track_metrics_host.cc:59: void
MediaStreamTrackMetricsHost::OnRemoveTrack(uint64 id) {
On 2014/07/23 15:53:42, Ronghua Wu wrote:
> curious, when will OnAddTrack and OnRemoveTrack be called?

When a track is added to peer connection.

https://codereview.chromium.org/411903002/diff/1/content/public/renderer/medi...
File content/public/renderer/media_stream_audio_sink.cc (right):

https://codereview.chromium.org/411903002/diff/1/content/public/renderer/medi...
content/public/renderer/media_stream_audio_sink.cc:22: LOG(ERROR) << "Only local
audio track is supported now";
On 2014/07/23 15:53:42, Ronghua Wu wrote:
> add info about what is "supported".
> 
> E.g. Can't add a remote track to a local stream.

Done.

https://codereview.chromium.org/411903002/diff/1/content/public/renderer/medi...
content/public/renderer/media_stream_audio_sink.cc:37: LOG(ERROR) << "Only local
audio track is supported now";
On 2014/07/23 15:53:42, Ronghua Wu wrote:
> dito

Done.

[no longer working on chromium, 2014-07-24 13:24:57]

Thanks Ronghua, PTAL.
FYI, I will be on parental leave from Tuesday, so it will be great if I can land
this ASAP and merge the fix the previous MSs.

[Ronghua Wu (Left Chromium), 2014-07-24 16:03:58]

LGTM

Please update the cl description as chatted offline to include the adding stream
to peerconnection case.

[no longer working on chromium, 2014-07-24 18:10:12]

The CQ bit was checked by xians@chromium.org

[commit-bot: I haz the power, 2014-07-24 18:11:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/xians@chromium.org/411903002/20001

[commit-bot: I haz the power, 2014-07-24 19:17:07]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  chromium_presubmit on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/chromium_presubmit/bu...)
  linux_chromium_rel_swarming on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_rel_sw...)

[commit-bot: I haz the power, 2014-07-24 19:23:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-07-24 19:23:06]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/chromium_presubmit/bu...)

[no longer working on chromium, 2014-07-25 08:20:58]

The CQ bit was checked by xians@chromium.org

[commit-bot: I haz the power, 2014-07-25 08:22:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/xians@chromium.org/411903002/20001

[commit-bot: I haz the power, 2014-07-25 08:23:55]

Change committed as 285528