Media Remoting: Add RemotingController.

media/base/mediaplayer_observer.h

+// Copyright 2016 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 MEDIA_BASE_MEDIAPLAYER_OBSERVER_H_

[xhwang, 2016/10/01 07:12:14]

nit: media and player are two words.

[xjz, 2016/10/03 22:31:08]

Renamed to MediaObserver.

+#define MEDIA_BASE_MEDIAPLAYER_OBSERVER_H_
+
+#include "base/callback.h"
+#include "media/base/audio_decoder_config.h"
+#include "media/base/cdm_context.h"
+#include "media/base/video_decoder_config.h"
+
+namespace media {
+
+// This class is an observer of media player events.
+class MEDIA_EXPORT MediaPlayerObserver {

[xhwang, 2016/10/01 07:12:14]

As commented before, we don't use "MediaPlayer" outside of media/blink. Also,
the concept of fullscreen doesn't belong to media/base layer as well. For the
former, how about just MediaObserver? We have a MediaObserver in
content/public/browser, but that shouldn't matter. For the latter, I don't have
any better idea at this moment :)

[xjz, 2016/10/03 22:31:08]

Renamed as "MediaObserver". 

+ public:
+  MediaPlayerObserver();
+  virtual ~MediaPlayerObserver();
+
+  // Called when the media element or its ancestor is entered/exited fullscreen.

[xhwang, 2016/10/01 07:12:14]

What if the ancestor (e.g. a <div>) entered fullscreen, but the media element
doesn't take 100% width/height of the <div>?

[xjz, 2016/10/03 22:31:08]

We currently treat this scenario same as the media element itself entering
fullscreen. It seems reasonable for normal video websites (such as vimeo,
youtube, etc.) . But We may add more criteria later if we find the logic doesn't
work well. Added some comments in RemotingController.h for this.

+  virtual void OnEnteredFullscreen() = 0;
+  virtual void OnExitedFullscreen() = 0;
+
+  // Called when CDM is attached to the media element.

[xhwang, 2016/10/01 07:12:14]

Add a comment that the |cdm_context| is only guaranteed to be valid in this
call.

[xjz, 2016/10/03 22:31:08]

Done.

+  virtual void OnSetCdm(CdmContext* cdm_context) = 0;
+
+  // Set video/audio config after demuxer is initialized.

[xhwang, 2016/10/01 07:12:14]

nit: "Set" is ambiguous. This is really just notify the observer. How about
"called when audio/video config is available after demuxer is initialized"?

[xjz, 2016/10/03 22:31:08]

Changed to pass PipelineMetadata instead to know if we have video/audio.

+  virtual void OnDecoderConfigChanged(
+      const AudioDecoderConfig& audio_config,
+      const VideoDecoderConfig& video_config) = 0;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_MEDIAPLAYER_OBSERVER_H_