Introduce WorkletGlobalScopeProxy interface.

third_party/WebKit/Source/modules/compositorworker/WindowCompositorWorklet.cpp

+// Copyright 2016 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 "modules/compositorworker/WindowCompositorWorklet.h"
+
+#include "core/frame/LocalDOMWindow.h"
+#include "core/frame/LocalFrame.h"
+#include "modules/compositorworker/CompositorWorklet.h"
+
+namespace blink {
+
+WindowCompositorWorklet::WindowCompositorWorklet(LocalDOMWindow& window)
+    : DOMWindowProperty(window.frame())
+{
+}
+
+const char* WindowCompositorWorklet::supplementName()
+{
+    return "WindowCompositorWorklet";
+}
+
+// static
+WindowCompositorWorklet& WindowCompositorWorklet::from(LocalDOMWindow& window)
+{
+    WindowCompositorWorklet* supplement = static_cast<WindowCompositorWorklet*>(Supplement<LocalDOMWindow>::from(window, supplementName()));
+    if (!supplement) {
+        supplement = new WindowCompositorWorklet(window);
+        provideTo(window, supplementName(), supplement);
+    }
+    return *supplement;
+}
+
+// static
+Worklet* WindowCompositorWorklet::compositorWorklet(ExecutionContext* executionContext, DOMWindow& window)
+{
+    return from(toLocalDOMWindow(window)).compositorWorklet(executionContext);
+}
+
+CompositorWorklet* WindowCompositorWorklet::compositorWorklet(ExecutionContext* executionContext) const
+{
+    if (!m_compositorWorklet && frame())
+        m_compositorWorklet = CompositorWorklet::create(frame(), executionContext);
+    return m_compositorWorklet.get();
+}
+
+DEFINE_TRACE(WindowCompositorWorklet)
+{
+    visitor->trace(m_compositorWorklet);
+    Supplement<LocalDOMWindow>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
+}
+
+} // namespace blink