[ServiceWorker] Make fetch() method better conformance with the spec.

Source/modules/serviceworkers/FetchManager.h

Index: Source/modules/serviceworkers/FetchManager.h
diff --git a/Source/modules/serviceworkers/FetchManager.h b/Source/modules/serviceworkers/FetchManager.h
index bfdfa7df6e8f07e3c95df6db4c0cc00cd13a4ed5..b6077f71f7e83a1c6a3edbbd693a2a0aab6f157f 100644
--- a/Source/modules/serviceworkers/FetchManager.h
+++ b/Source/modules/serviceworkers/FetchManager.h
@@ -12,6 +12,7 @@
 namespace WebCore {
 
 class ExecutionContext;
+class FetchRequestData;
 class ScriptState;
 class ResourceRequest;
 
@@ -19,7 +20,7 @@ class FetchManager {
 public:
     FetchManager(ExecutionContext*);
     ~FetchManager();
-    ScriptPromise fetch(ScriptState*, PassOwnPtr<ResourceRequest>);
+    ScriptPromise fetch(ScriptState*, PassRefPtr<FetchRequestData>);
 
     static bool isSimpleMethod(const String&);
     static bool isForbiddenMethod(const String&);