MediaRecorder: make MediaRecorderHandler a MediaStreamObserver

content/public/renderer/media_stream_api.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_API_H_
 #define CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_API_H_
 
 #include "content/common/content_export.h"
 #include "media/base/audio_capturer_source.h"
 #include "media/base/video_capturer_source.h"
@@ skipping 31 matching lines @@
     const media::AudioParameters& params,
     bool is_remote,
     bool is_readonly,
     const std::string& media_stream_url);
 CONTENT_EXPORT bool AddAudioTrackToMediaStream(
     const scoped_refptr<media::AudioCapturerSource>& source,
     bool is_remote,
     bool is_readonly,
     blink::WebMediaStream* web_stream);
 
+CONTENT_EXPORT void AddMediaStreamTowebMediaStream(
+    blink::WebMediaStream* web_stream);

[perkj_chrome, 2016/01/07 09:18:00]

?

[mcasas, 2016/01/08 00:14:12]

Following the previous explanation, WebTestDelegate is
implemented in 
content/shell/renderer/layout_tests/blink_test_runner.h,
that can only depend on content/public. And I don't
think MediaStream class should be there, instead the
pattern followed is to use media_stream_api.{cc,h} to
"implement" the calls from the WebTestDelegate in a
correct fashion (e.g.
BlinkTestRunner::AddMediaStreamVideoSourceAndTrack() 
etc).

So WebTestDelegate --> BlinkTestRunner --...
-->content/public/renderer/media_stream_api --...
--> content/renderer/media/ real stuff.

But fret not, since this CL will need the approval of
e.g. jochen@ and those points will be reviewed in 
more depth.

+
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_API_H_