Decouple MediaSession messages from WebContents (full patch)

content/browser/media/session/media_session.h

Index: content/browser/media/session/media_session.h
diff --git a/content/browser/media/session/media_session.h b/content/browser/media/session/media_session.h
deleted file mode 100644
index 9239c7854a18b18326e2c2983451e49490922982..0000000000000000000000000000000000000000
--- a/content/browser/media/session/media_session.h
+++ /dev/null
@@ -1,245 +0,0 @@
-// 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_BROWSER_MEDIA_SESSION_MEDIA_SESSION_H_
-#define CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_H_
-
-#include <stddef.h>
-
-#include "base/callback_list.h"
-#include "base/id_map.h"
-#include "base/macros.h"
-#include "base/optional.h"
-#include "content/browser/media/session/audio_focus_manager.h"
-#include "content/browser/media/session/media_session_uma_helper.h"
-#include "content/common/content_export.h"
-#include "content/public/browser/web_contents_observer.h"
-#include "content/public/browser/web_contents_user_data.h"
-#include "content/public/common/media_metadata.h"
-
-class MediaSessionBrowserTest;
-
-namespace media {
-enum class MediaContentType;
-}  // namespace media
-
-namespace content {
-
-class AudioFocusDelegate;
-class AudioFocusManagerTest;
-class MediaSessionPlayerObserver;
-class MediaSessionStateObserver;
-class MediaSessionVisibilityBrowserTest;
-
-// MediaSession manages the media session and audio focus for a given
-// WebContents. It is requesting the audio focus, pausing when requested by the
-// system and dropping it on demand.
-// The audio focus can be of two types: Transient or Content. A Transient audio
-// focus will allow other players to duck instead of pausing and will be
-// declared as temporary to the system. A Content audio focus will not be
-// declared as temporary and will not allow other players to duck. If a given
-// WebContents can only have one audio focus at a time, it will be Content in
-// case of Transient and Content audio focus are both requested.
-// TODO(thakis,mlamouri): MediaSession isn't CONTENT_EXPORT'd because it creates
-// complicated build issues with WebContentsUserData being a non-exported
-// template, see htttps://crbug.com/589840. As a result, the class uses
-// CONTENT_EXPORT for methods that are being used from tests. CONTENT_EXPORT
-// should be moved back to the class when the Windows build will work with it.
-class MediaSession : public WebContentsObserver,
-                     protected WebContentsUserData<MediaSession> {
- public:
-  enum class SuspendType {
-    // Suspended by the system because a transient sound needs to be played.
-    SYSTEM,
-    // Suspended by the UI.
-    UI,
-    // Suspended by the page via script or user interaction.
-    CONTENT,
-  };
-
-  // Only visible to tests.
-  enum class State {
-    ACTIVE,
-    SUSPENDED,
-    INACTIVE
-  };
-
-  // Returns the MediaSession associated to this WebContents. Creates one if
-  // none is currently available.
-  CONTENT_EXPORT static MediaSession* Get(WebContents* web_contents);
-
-  ~MediaSession() override;
-
-  void SetMetadata(const base::Optional<MediaMetadata>& metadata);
-  const base::Optional<MediaMetadata>& metadata() const { return metadata_; }
-
-  // Adds the given player to the current media session. Returns whether the
-  // player was successfully added. If it returns false, AddPlayer() should be
-  // called again later.
-  CONTENT_EXPORT bool AddPlayer(MediaSessionPlayerObserver* observer,
-                                int player_id,
-                                media::MediaContentType media_content_type);
-
-  // Removes the given player from the current media session. Abandons audio
-  // focus if that was the last player in the session.
-  CONTENT_EXPORT void RemovePlayer(MediaSessionPlayerObserver* observer,
-                                   int player_id);
-
-  // Removes all the players associated with |observer|. Abandons audio focus if
-  // these were the last players in the session.
-  CONTENT_EXPORT void RemovePlayers(MediaSessionPlayerObserver* observer);
-
-  // Record that the session was ducked.
-  void RecordSessionDuck();
-
-  // Called when a player is paused in the content.
-  // If the paused player is the last player, we suspend the MediaSession.
-  // Otherwise, the paused player will be removed from the MediaSession.
-  CONTENT_EXPORT void OnPlayerPaused(MediaSessionPlayerObserver* observer,
-                                     int player_id);
-
-  // Resume the media session.
-  // |type| represents the origin of the request.
-  CONTENT_EXPORT void Resume(SuspendType suspend_type);
-
-  // Suspend the media session.
-  // |type| represents the origin of the request.
-  CONTENT_EXPORT void Suspend(SuspendType suspend_type);
-
-  // Stop the media session.
-  // |type| represents the origin of the request.
-  CONTENT_EXPORT void Stop(SuspendType suspend_type);
-
-  // Let the media session start ducking such that the volume multiplier is
-  // reduced.
-  CONTENT_EXPORT void StartDucking();
-
-  // Let the media session stop ducking such that the volume multiplier is
-  // recovered.
-  CONTENT_EXPORT void StopDucking();
-
-  // Returns if the session can be controlled by Resume() and Suspend calls
-  // above.
-  CONTENT_EXPORT bool IsControllable() const;
-
-  // Returns if the session is currently active.
-  CONTENT_EXPORT bool IsActive() const;
-
-  // Returns if the session is currently suspended.
-  // TODO(mlamouri): IsSuspended() below checks if the state is not ACTIVE
-  // instead of checking if the state is SUSPENDED. In order to not have to
-  // change all the callers and make the current refactoring ridiculously huge,
-  // this method is introduced temporarily and will be removed later.
-  CONTENT_EXPORT bool IsReallySuspended() const;
-
-  // Returns if the session is currently suspended or inactive.
-  CONTENT_EXPORT bool IsSuspended() const;
-
-  // Returns the audio focus type. The type is updated everytime after the
-  // session requests audio focus.
-  CONTENT_EXPORT AudioFocusManager::AudioFocusType audio_focus_type() const {
-    return audio_focus_type_;
-  }
-
-  // Returns whether the session has Pepper instances.
-  bool HasPepper() const;
-
-  // WebContentsObserver implementation
-  void WebContentsDestroyed() override;
-
- private:
-  friend class content::WebContentsUserData<MediaSession>;
-  friend class ::MediaSessionBrowserTest;
-  friend class content::MediaSessionVisibilityBrowserTest;
-  friend class content::AudioFocusManagerTest;
-  friend class content::MediaSessionStateObserver;
-
-  CONTENT_EXPORT void SetDelegateForTests(
-      std::unique_ptr<AudioFocusDelegate> delegate);
-  CONTENT_EXPORT bool IsActiveForTest() const;
-  CONTENT_EXPORT void RemoveAllPlayersForTest();
-  CONTENT_EXPORT MediaSessionUmaHelper* uma_helper_for_test();
-
-  // Representation of a player for the MediaSession.
-  struct PlayerIdentifier {
-    PlayerIdentifier(MediaSessionPlayerObserver* observer, int player_id);
-    PlayerIdentifier(const PlayerIdentifier&) = default;
-
-    void operator=(const PlayerIdentifier&) = delete;
-    bool operator==(const PlayerIdentifier& player_identifier) const;
-
-    // Hash operator for base::hash_map<>.
-    struct Hash {
-      size_t operator()(const PlayerIdentifier& player_identifier) const;
-    };
-
-    MediaSessionPlayerObserver* observer;
-    int player_id;
-  };
-  using PlayersMap = base::hash_set<PlayerIdentifier, PlayerIdentifier::Hash>;
-  using StateChangedCallback = base::Callback<void(State)>;
-
-  CONTENT_EXPORT explicit MediaSession(WebContents* web_contents);
-
-  void Initialize();
-
-  CONTENT_EXPORT void OnSuspendInternal(SuspendType suspend_type,
-                                        State new_state);
-  CONTENT_EXPORT void OnResumeInternal(SuspendType suspend_type);
-
-  // Requests audio focus to the AudioFocusDelegate.
-  // Returns whether the request was granted.
-  CONTENT_EXPORT bool RequestSystemAudioFocus(
-      AudioFocusManager::AudioFocusType audio_focus_type);
-
-  // To be called after a call to AbandonAudioFocus() in order request the
-  // delegate to abandon the audio focus.
-  CONTENT_EXPORT void AbandonSystemAudioFocusIfNeeded();
-
-  // Notifies WebContents about the state change of the media session.
-  void UpdateWebContents();
-
-  // Internal method that should be used instead of setting audio_focus_state_.
-  // It sets audio_focus_state_ and notifies observers about the state change.
-  void SetAudioFocusState(State audio_focus_state);
-
-  // Update the volume multiplier when ducking state changes.
-  void UpdateVolumeMultiplier();
-
-  // Get the volume multiplier, which depends on whether the media session is
-  // ducking.
-  double GetVolumeMultiplier() const;
-
-  // Registers a MediaSession state change callback.
-  CONTENT_EXPORT std::unique_ptr<base::CallbackList<void(State)>::Subscription>
-  RegisterMediaSessionStateChangedCallbackForTest(
-      const StateChangedCallback& cb);
-
-  CONTENT_EXPORT bool AddPepperPlayer(MediaSessionPlayerObserver* observer,
-                                      int player_id);
-
-  std::unique_ptr<AudioFocusDelegate> delegate_;
-  PlayersMap players_;
-  PlayersMap pepper_players_;
-
-  State audio_focus_state_;
-  SuspendType suspend_type_;
-  AudioFocusManager::AudioFocusType audio_focus_type_;
-
-  MediaSessionUmaHelper uma_helper_;
-
-  // The ducking state of this media session. The initial value is |false|, and
-  // is set to |true| after StartDucking(), and will be set to |false| after
-  // StopDucking().
-  bool is_ducking_;
-
-  base::Optional<MediaMetadata> metadata_;
-  base::CallbackList<void(State)> media_session_state_listeners_;
-
-  DISALLOW_COPY_AND_ASSIGN(MediaSession);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_H_