[part 2] Make classes and structures in modules fast-allocated.

Source/modules/mediasession/HTMLMediaElementMediaSession.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 HTMLMediaElementMediaSession_h
 #define HTMLMediaElementMediaSession_h
 
 #include "core/html/HTMLMediaElement.h"
 #include "modules/ModulesExport.h"
 #include "modules/mediasession/MediaSession.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 // A supplement to HTMLMediaElement responsible for the integration of
 // MediaSession with HTMLMediaElement.
 class HTMLMediaElementMediaSession final : public NoBaseWillBeGarbageCollected<HTMLMediaElementMediaSession>, public WillBeHeapSupplement<HTMLMediaElement> {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(HTMLMediaElementMediaSession);
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(HTMLMediaElementMediaSession);
 public:
     static MediaSession* session(HTMLMediaElement&);
     static void setSession(HTMLMediaElement&, MediaSession*);
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     static HTMLMediaElementMediaSession& from(HTMLMediaElement&);
     static HTMLMediaElementMediaSession* fromIfExists(HTMLMediaElement&);
     static const char* supplementName();
 
     PersistentWillBeMember<MediaSession> m_session;
 };
 
 } // namespace blink
 
 #endif // HTMLMediaElementMediaSession_h