[worklets] Introduce ThreadedWorkletMessagingProxy and AnimationWorkletMessagaingProxy.

third_party/WebKit/Source/core/workers/ThreadedWorkletGlobalScopeProxy.h

 // 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 ThreadedWorkletGlobalScopeProxy_h
 #define ThreadedWorkletGlobalScopeProxy_h
 
 #include "core/workers/WorkletGlobalScopeProxy.h"
 
+// TODO(ikilpatrick): remove this file once AudioWorklet is no longer using it.
+
 namespace blink {
 
 class ThreadedWorkletGlobalScopeProxy : public WorkletGlobalScopeProxy {
 public:
-    void evaluateScript(const ScriptSourceCode&) final
-    {
-        // TODO(ikilpatrick): implement.
-    }
-
-    void terminateWorkletGlobalScope() final
-    {
-        // TODO(ikilpatrick): implement.
-    }
+    void evaluateScript(const ScriptSourceCode&) final {}
+    void terminateWorkletGlobalScope() final {}
 };
 
 } // namespace blink
 
 #endif // ThreadedWorkletGlobalScopeProxy_h