Provide a WebContents API to discover the playback of a fullscreen video.

content/browser/media/media_web_contents_observer.h

 // Copyright 2014 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_BROWSER_MEDIA_MEDIA_WEB_CONTENTS_OBSERVER_H_
 #define CONTENT_BROWSER_MEDIA_MEDIA_WEB_CONTENTS_OBSERVER_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 24 matching lines @@
 // forwards them to the corresponding managers. The managers are responsible
 // for sending IPCs back to the RenderFrameObservers at the render side.
 class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
  public:
   explicit MediaWebContentsObserver(WebContents* web_contents);
   ~MediaWebContentsObserver() override;
 
   // Called by WebContentsImpl when the audible state may have changed.
   void MaybeUpdateAudibleState();
 
+  // Called by WebContentsImpl to know if an active player is currently
+  // fullscreen dominant.
+  // It should only be called while the WebContents is fullscreen.
+  bool HasActiveFullscreenDominantVideo() const;

[liberato (no reviews please), 2017/02/14 23:00:01]

naming is a little confusing.

personally, i'd go more for something like this:

- remove 'dominant' from the name - maybe HasActiveEffectivelyFullscreenVideo()
or similar.
- returns 'no' if webcontents isn't full screen, rather than dcheck.

otherwise, 'dominant' and/or 'fullscreen' seem overloaded.

as in, the caller wants to know 'is the user looking at a really big video in
this webcontents right now?'

[mlamouri (slow - plz ping), 2017/02/17 16:36:24]

Renamed to `HasActiveEffectivelyFullscreenVideo`. It's quite better :)

+
   // WebContentsObserver implementation.
   void WebContentsDestroyed() override;
   void RenderFrameDeleted(RenderFrameHost* render_frame_host) override;
   bool OnMessageReceived(const IPC::Message& message,
                          RenderFrameHost* render_frame_host) override;
   void WasShown() override;
   void WasHidden() override;
 
   bool has_audio_power_save_blocker_for_testing() const {
     return !!audio_power_save_blocker_;
@@ skipping 12 matching lines @@
   void OnMediaDestroyed(RenderFrameHost* render_frame_host, int delegate_id);
   void OnMediaPaused(RenderFrameHost* render_frame_host,
                      int delegate_id,
                      bool reached_end_of_stream);
   void OnMediaPlaying(RenderFrameHost* render_frame_host,
                       int delegate_id,
                       bool has_video,
                       bool has_audio,
                       bool is_remote,
                       media::MediaContentType media_content_type);
+  void OnMediaFullscreenChange(RenderFrameHost* render_frame_host,
+                               int delegate_id,
+                               bool is_fullscreen);
+  void OnMediaDominantChange(RenderFrameHost* render_frame_host,
+                             int delegate_id,
+                             bool is_dominant);
 
   // Clear |render_frame_host|'s tracking entry for its power save blockers.
   void ClearPowerSaveBlockers(RenderFrameHost* render_frame_host);
 
   // Creates an audio or video power save blocker respectively.
   void CreateAudioPowerSaveBlocker();
   void CreateVideoPowerSaveBlocker();
 
   // Releases the audio power save blockers if |active_audio_players_| is empty.
   // Likewise, releases the video power save blockers if |active_video_players_|
@@ skipping 13 matching lines @@
   void RemoveAllMediaPlayerEntries(RenderFrameHost* render_frame_host,
                                    ActiveMediaPlayerMap* player_map,
                                    std::set<MediaPlayerId>* removed_players);
 
   // Tracking variables and associated power save blockers for media playback.
   ActiveMediaPlayerMap active_audio_players_;
   ActiveMediaPlayerMap active_video_players_;
   std::unique_ptr<device::PowerSaveBlocker> audio_power_save_blocker_;
   std::unique_ptr<device::PowerSaveBlocker> video_power_save_blocker_;
 
+  // FullscreenDominantInfo keeps track of whether a MediaPlayerId is fullscreen
+  // or dominant inside a fullscreen frame.
+  struct FullscreenDominantInfo {
+    FullscreenDominantInfo() = delete;
+    FullscreenDominantInfo(const FullscreenDominantInfo&) = default;
+    FullscreenDominantInfo& operator=(const FullscreenDominantInfo&) = default;
+
+    FullscreenDominantInfo(bool fullscreen, bool dominant)
+        : fullscreen(fullscreen), dominant(dominant) {}
+
+    bool fullscreen = false;
+    bool dominant = false;
+  };
+
+  // If the |MediaPlayerId| is set to |{ nullptr, 0 }|, |FullscreenDominantInfo|
+  // should be ignored.
+  std::pair<MediaPlayerId, FullscreenDominantInfo> fullscreen_dominant_video_ =

[liberato (no reviews please), 2017/02/14 23:00:01]

nit: perhaps move MediaPlayerId into FullscreenDominantInfo.  all of the
'.first.first' are a bit confusing.

[mlamouri (slow - plz ping), 2017/02/17 16:36:24]

I switched to base::Optional<MediaPlayerId>. Should be simpler :)

+      {{nullptr, 0}, FullscreenDominantInfo(false, false)};
+
   MediaSessionControllersManager session_controllers_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaWebContentsObserver);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_MEDIA_WEB_CONTENTS_OBSERVER_H_