Hook up RendererMediaSessionManager with browser side

third_party/WebKit/public/platform/modules/mediasession/WebMediaSession.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 WebMediaSession_h
 #define WebMediaSession_h
 
 #include "public/platform/WebCallbacks.h"
 #include "public/platform/modules/mediasession/WebMediaSessionError.h"
 
 namespace blink {
 
 using WebMediaSessionActivateCallback = WebCallbacks<void, const WebMediaSessionError&>;
 using WebMediaSessionDeactivateCallback = WebCallbacks<void, void>;
 
 struct WebMediaMetadata;
 
 class WebMediaSession {
 public:
     virtual ~WebMediaSession() = default;
 
+    // Tries to activate the session by requesting audio focus from
+    // the system. May fail if audio focus is denied by the
+    // system. The ownership of the pointer is transferred to the
+    // WebMediaSession implementation.
     virtual void activate(WebMediaSessionActivateCallback*) = 0;
+
+    // Deactivates the session by abandoning audio focus. Will not
+    // fail in way visible to the user of the WebMediaSession. The
+    // ownership of the pointer is transferred to the WebMediaSession
+    // implementation.
     virtual void deactivate(WebMediaSessionDeactivateCallback*) = 0;
 
     // Updates the metadata associated with the WebMediaSession. The metadata
     // can be a nullptr in which case the associated metadata should be reset.
     // The pointer is not owned by the WebMediaSession implementation.
     virtual void setMetadata(const WebMediaMetadata*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebMediaSession_h