Use UUID for ServiceWorker Client identifier (1/3, blink)

Source/modules/serviceworkers/ServiceWorkerClient.h

 // Copyright 2014 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 ServiceWorkerClient_h
 #define ServiceWorkerClient_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "bindings/core/v8/SerializedScriptValue.h"
@@ skipping 16 matching lines @@
     // Client.idl
     String url() const { return m_url; }
     void postMessage(ExecutionContext*, PassRefPtr<SerializedScriptValue> message, const MessagePortArray*, ExceptionState&);
 
     DEFINE_INLINE_VIRTUAL_TRACE() { }
 
 protected:
     explicit ServiceWorkerClient(const WebServiceWorkerClientInfo&);
 
     unsigned id() const { return m_id; }
+    String uuid() const { return m_uuid; }
 
 private:
-    unsigned m_id;
+    unsigned m_id; // FIXME: Deprecate this when we switch to UUID.
+    String m_uuid;
     String m_url;
 };
 
 } // namespace blink
 
 #endif // ServiceWorkerClient_h