First version of PerformanceObserver

Source/core/timing/PerformanceObserverCallback.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 PerformanceObserverCallback_h
+#define PerformanceObserverCallback_h
+
+#include "platform/heap/Handle.h"
+#include "wtf/RefPtr.h"
+
+namespace blink {
+
+class ExecutionContext;
+class PerformanceObserverEntryList;
+class PerformanceObserver;
+
+class PerformanceObserverCallback : public GarbageCollectedFinalized<PerformanceObserverCallback> {
+public:
+    virtual ~PerformanceObserverCallback() { }
+
+    virtual void handleEvent(PerformanceObserverEntryList*, PerformanceObserver*) = 0;
+    virtual ExecutionContext* executionContext() const = 0;
+
+    DEFINE_INLINE_VIRTUAL_TRACE() { }
+};
+
+}
+
+#endif // PerformanceObserverCallback_h