Decouple performance() from LocalDOMWindow

Source/core/timing/DOMWindowPerformance.cpp

Index: Source/core/timing/DOMWindowPerformance.cpp
diff --git a/Source/core/timing/DOMWindowPerformance.cpp b/Source/core/timing/DOMWindowPerformance.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5eed269fdfc5f45e9a43c7c5546439263ddfce5f
--- /dev/null
+++ b/Source/core/timing/DOMWindowPerformance.cpp
@@ -0,0 +1,59 @@
+// 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.
+
+#include "config.h"
+#include "core/timing/DOMWindowPerformance.h"
+
+#include "core/frame/LocalDOMWindow.h"
+#include "core/frame/LocalFrame.h"
+#include "core/timing/Performance.h"
+
+namespace blink {
+
+DOMWindowPerformance::DOMWindowPerformance(LocalDOMWindow& window)
+    : DOMWindowProperty(window.frame())
+    , m_window(window)
+{
+}
+
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(DOMWindowPerformance);
+
+void DOMWindowPerformance::trace(Visitor* visitor)
+{
+    visitor->trace(m_performance);
+    WillBeHeapSupplement<LocalDOMWindow>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
+}
+
+// static
+const char* DOMWindowPerformance::supplementName()
+{
+    return "DOMWindowPerformance";
+}
+
+// static
+DOMWindowPerformance& DOMWindowPerformance::from(LocalDOMWindow& window)
+{
+    DOMWindowPerformance* supplement = static_cast<DOMWindowPerformance*>(WillBeHeapSupplement<LocalDOMWindow>::from(window, supplementName()));
+    if (!supplement) {
+        supplement = new DOMWindowPerformance(window);
+        provideTo(window, supplementName(), adoptPtrWillBeNoop(supplement));
+    }
+    return *supplement;
+}
+
+// static
+Performance* DOMWindowPerformance::performance(DOMWindow& window)
+{
+    return from(toLocalDOMWindow(window)).performance();
+}
+
+Performance* DOMWindowPerformance::performance()
+{
+    if (!m_performance)
+        m_performance = Performance::create(m_window.frame());
+    return m_performance.get();
+}
+
+} // namespace blink