Oilpan: fix build after r198049.

Source/modules/mediasession/MediaSession.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 MediaSession_h
 #define MediaSession_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
-class MediaSession : public ScriptWrappable, public RefCountedWillBeNoBase<MediaSession> {
+class MediaSession : public GarbageCollected<MediaSession>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static RefPtrWillBeRawPtr<MediaSession> create();
+    static MediaSession* create();
 
     void activate();
     void deactivate();
 
+    DEFINE_INLINE_TRACE() { }
+
 private:
     MediaSession();
 };
 
-}
+} // namespace blink
 
 #endif // MediaSession_h