Introduce WorkletGlobalScopeProxy interface.

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

Index: third_party/WebKit/Source/modules/compositorworker/WindowCompositorWorklet.h
diff --git a/third_party/WebKit/Source/modules/compositorworker/WindowCompositorWorklet.h b/third_party/WebKit/Source/modules/compositorworker/WindowCompositorWorklet.h
new file mode 100644
index 0000000000000000000000000000000000000000..69f33477261282fc56c5e2eef21cb9556189cdaf
--- /dev/null
+++ b/third_party/WebKit/Source/modules/compositorworker/WindowCompositorWorklet.h
@@ -0,0 +1,38 @@
+// 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.
+
+#ifndef WindowCompositorWorklet_h
+#define WindowCompositorWorklet_h
+
+#include "core/frame/DOMWindowProperty.h"
+#include "modules/ModulesExport.h"
+#include "platform/Supplementable.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class DOMWindow;
+class ExecutionContext;
+class CompositorWorklet;
+class Worklet;
+
+class MODULES_EXPORT WindowCompositorWorklet final : public GarbageCollected<WindowCompositorWorklet>, public Supplement<LocalDOMWindow>, public DOMWindowProperty {
+    USING_GARBAGE_COLLECTED_MIXIN(WindowCompositorWorklet);
+public:
+    static WindowCompositorWorklet& from(LocalDOMWindow&);
+    static Worklet* compositorWorklet(ExecutionContext*, DOMWindow&);
+    CompositorWorklet* compositorWorklet(ExecutionContext*) const;
+
+    DECLARE_TRACE();
+
+private:
+    explicit WindowCompositorWorklet(LocalDOMWindow&);
+    static const char* supplementName();
+
+    mutable Member<CompositorWorklet> m_compositorWorklet;
+};
+
+} // namespace blink
+
+#endif // WindowCompositorWorklet_h