Decouple MediaSession messages from WebContents (full patch)

content/public/browser/media_session.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 CONTENT_PUBLIC_BROWSER_MEDIA_SESSION_H_
+#define CONTENT_PUBLIC_BROWSER_MEDIA_SESSION_H_
+
+#include "base/macros.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class WebContents;
+
+// MediaSession manages the media session and audio focus for a given
+// WebContents. There is only one MediaSession per WebContents.
+//
+// MediaSession allows clients to observe its changes via MediaSessionObserver,
+// and allows clients to resume/suspend/stop the managed players.
+class 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,
+  };
+
+  // Returns the MediaSession associated to this WebContents. Creates one if
+  // none is currently available.
+  CONTENT_EXPORT static MediaSession* Get(WebContents* contents);
+
+  virtual ~MediaSession() = default;
+
+  // Resume the media session.
+  // |type| represents the origin of the request.
+  virtual void Resume(SuspendType suspend_type) = 0;
+
+  // Resume the media session.
+  // |type| represents the origin of the request.
+  virtual void Suspend(SuspendType suspend_type) = 0;
+
+  // Resume the media session.
+  // |type| represents the origin of the request.
+  virtual void Stop(SuspendType suspend_type) = 0;
+
+ protected:
+  MediaSession() = default;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_MEDIA_SESSION_H_