[Blink>MediaSession] Use setActionCallback() instead of event listeners for media control actions

content/browser/media/session/media_session_service_impl.cc

 // 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.
 
 #include "content/browser/media/session/media_session_service_impl.h"
 
 #include "content/browser/media/session/media_metadata_sanitizer.h"
 #include "content/browser/media/session/media_session_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/browser_thread.h"
@@ skipping 50 matching lines @@
   }
   metadata_ = metadata;
 
   MediaSessionImpl* session = GetMediaSession();
   if (session)
     session->OnMediaSessionMetadataChanged(this);
 }
 
 void MediaSessionServiceImpl::EnableAction(
     blink::mojom::MediaSessionAction action) {
+  // Action already enabled
+  if (actions_.find(action) != actions_.end())
+    return;
+
   actions_.insert(action);
   MediaSessionImpl* session = GetMediaSession();
   if (session)
     session->OnMediaSessionActionsChanged(this);
 }
 
 void MediaSessionServiceImpl::DisableAction(
     blink::mojom::MediaSessionAction action) {
+  // Action already disabled
+  if (actions_.find(action) == actions_.end())
+    return;
+
   actions_.erase(action);
   MediaSessionImpl* session = GetMediaSession();
   if (session)
     session->OnMediaSessionActionsChanged(this);
 }
 
 MediaSessionImpl* MediaSessionServiceImpl::GetMediaSession() {
   WebContentsImpl* contents = static_cast<WebContentsImpl*>(
       WebContentsImpl::FromRenderFrameHost(render_frame_host_));
   if (!contents)
     return nullptr;
   return MediaSessionImpl::Get(contents);
 }
 
 void MediaSessionServiceImpl::Bind(
     blink::mojom::MediaSessionServiceRequest request) {
   binding_.reset(new mojo::Binding<blink::mojom::MediaSessionService>(
       this, std::move(request)));
 }
 
 }  // namespace content