[ServiceWorker] Make Request class better conformance with the spec.

Source/platform/exported/WebServiceWorkerRequest.cpp

Index: Source/platform/exported/WebServiceWorkerRequest.cpp
diff --git a/Source/platform/exported/WebServiceWorkerRequest.cpp b/Source/platform/exported/WebServiceWorkerRequest.cpp
index 70fdc7d861ccd4d9d52b3dc570701a864b45e414..fdeb81a925ed4276e83d60a09e548cc655b62902 100644
--- a/Source/platform/exported/WebServiceWorkerRequest.cpp
+++ b/Source/platform/exported/WebServiceWorkerRequest.cpp
@@ -10,12 +10,11 @@ namespace blink {
 class WebServiceWorkerRequestPrivate : public RefCounted<WebServiceWorkerRequestPrivate> {
 public:
     WebServiceWorkerRequestPrivate()
-        : isReload(false)
-    {
-    }
+        : isReload(false) { }
     WebURL url;
     WebString method;
-    HashMap<String, String> headers;
+    Vector<OwnPtr<WebServiceWorkerRequest::Header> > headerList;
+    WebString referrer;
     bool isReload;
 };
 
@@ -56,12 +55,22 @@ WebString WebServiceWorkerRequest::method() const
 
 void WebServiceWorkerRequest::setHeader(const WebString& key, const WebString& value)
 {
-    m_private->headers.set(key, value);
+    m_private->headerList.append(adoptPtr(new Header(key, value)));
 }
 
-const HashMap<String, String>& WebServiceWorkerRequest::headers() const
+const Vector<OwnPtr<WebServiceWorkerRequest::Header> >& WebServiceWorkerRequest::headerList() const
 {
-    return m_private->headers;
+    return m_private->headerList;
+}
+
+void WebServiceWorkerRequest::setReferrer(const WebString& referrer)
+{
+    m_private->referrer = referrer;
+}
+
+WebString WebServiceWorkerRequest::referrer() const
+{
+    return m_private->referrer;
 }
 
 void WebServiceWorkerRequest::setIsReload(bool isReload)