Simplify WebServiceWorker{Registration}Proxy interfaces.

Source/modules/serviceworkers/ServiceWorkerRegistration.cpp

Index: Source/modules/serviceworkers/ServiceWorkerRegistration.cpp
diff --git a/Source/modules/serviceworkers/ServiceWorkerRegistration.cpp b/Source/modules/serviceworkers/ServiceWorkerRegistration.cpp
index 999df873b2cd8487d0d6f81d3a3195d22beb8d7d..98eb6182cc78029cf6382b6f68f193b5970bb6ee 100644
--- a/Source/modules/serviceworkers/ServiceWorkerRegistration.cpp
+++ b/Source/modules/serviceworkers/ServiceWorkerRegistration.cpp
@@ -126,13 +126,10 @@ ServiceWorkerRegistration* ServiceWorkerRegistration::getOrCreate(ExecutionConte
     if (!outerRegistration)
         return 0;
 
-    WebServiceWorkerRegistrationProxy* proxy = outerRegistration->proxy();
-    if (proxy) {
-        ServiceWorkerRegistration* existingRegistration = *proxy;
-        if (existingRegistration) {
-            ASSERT(existingRegistration->executionContext() == executionContext);
-            return existingRegistration;
-        }
+    ServiceWorkerRegistration* existingRegistration = static_cast<ServiceWorkerRegistration*>(outerRegistration->proxy());
+    if (existingRegistration) {
+        ASSERT(existingRegistration->executionContext() == executionContext);
+        return existingRegistration;
     }
 
     ServiceWorkerRegistration* registration = new ServiceWorkerRegistration(executionContext, adoptPtr(outerRegistration));
@@ -142,7 +139,6 @@ ServiceWorkerRegistration* ServiceWorkerRegistration::getOrCreate(ExecutionConte
 
 ServiceWorkerRegistration::ServiceWorkerRegistration(ExecutionContext* executionContext, PassOwnPtr<WebServiceWorkerRegistration> outerRegistration)
     : ActiveDOMObject(executionContext)
-    , WebServiceWorkerRegistrationProxy(this)
     , m_outerRegistration(outerRegistration)
     , m_provider(0)
     , m_stopped(false)