Oilpan: fix build after r177450.

Source/bindings/core/v8/ScriptPromisePropertyBase.h

 // Copyright 2014 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 ScriptPromisePropertyBase_h
 #define ScriptPromisePropertyBase_h
 
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseProperties.h"
 #include "core/dom/ContextLifecycleObserver.h"
 #include "wtf/RefCounted.h"
 #include <v8.h>
 
 namespace WebCore {
 
 class ExecutionContext;
 
-class ScriptPromisePropertyBase : public ContextLifecycleObserver, public RefCounted<ScriptPromisePropertyBase> {
+class ScriptPromisePropertyBase : public RefCountedWillBeRefCountedGarbageCollected<ScriptPromisePropertyBase>, public ContextLifecycleObserver {
 public:
     virtual ~ScriptPromisePropertyBase();
 
     enum Name {
 #define P(Name) Name
         SCRIPT_PROMISE_PROPERTIES(P)
 #undef P
     };
 
     enum State {
         Pending,
         Resolved,
         Rejected,
     };
     State state() const { return m_state; }
 
     ScriptPromise promise(DOMWrapperWorld&);
 
+    virtual void trace(Visitor*) { }
+
 protected:
     ScriptPromisePropertyBase(ExecutionContext*, Name);
 
     void resolveOrReject(State targetState);
 
     // ScriptPromiseProperty overrides these to wrap the holder,
     // rejected value and resolved value. The
     // ScriptPromisePropertyBase caller will enter the V8Context for
     // the property's execution context and the world it is
     // creating/settling promises in; the implementation should use
@@ skipping 13 matching lines @@
     State m_state;
 
     // FIXME: When isolated worlds are supported replace this with a
     // set of wrappers.
     ScopedPersistent<v8::Object> m_mainWorldWrapper;
 };
 
 } // namespace WebCore
 
 #endif // ScriptPromisePropertyBase_h