Add the navigator.serviceWorker.waiting property.

Source/modules/serviceworkers/ServiceWorkerContainer.h

Index: Source/modules/serviceworkers/ServiceWorkerContainer.h
diff --git a/Source/modules/serviceworkers/ServiceWorkerContainer.h b/Source/modules/serviceworkers/ServiceWorkerContainer.h
index 253aa4a4fd97cc590ca26e8581aa1d92c4062cfd..d098ff775b1609770014b9f95c5e8ee756da9958 100644
--- a/Source/modules/serviceworkers/ServiceWorkerContainer.h
+++ b/Source/modules/serviceworkers/ServiceWorkerContainer.h
@@ -64,6 +64,7 @@ public:
 
     void detachClient();
 
+    PassRefPtrWillBeRawPtr<ServiceWorker> waiting() { return m_waiting.get(); }
     PassRefPtrWillBeRawPtr<ServiceWorker> controller() { return m_controller.get(); }
     ScriptPromise ready(ScriptState*);
 
@@ -71,6 +72,7 @@ public:
     ScriptPromise unregisterServiceWorker(ScriptState*, const String& scope = String());
 
     // WebServiceWorkerProviderClient overrides.
+    virtual void setWaiting(blink::WebServiceWorker*) OVERRIDE;
     virtual void setController(blink::WebServiceWorker*) OVERRIDE;
     virtual void dispatchMessageEvent(const blink::WebString& message, const blink::WebMessagePortChannelArray&) OVERRIDE;
 
@@ -81,6 +83,7 @@ private:
     explicit ServiceWorkerContainer(ExecutionContext*);
 
     blink::WebServiceWorkerProvider* m_provider;
+    RefPtr<ServiceWorker> m_waiting;
     RefPtr<ServiceWorker> m_controller;
 };