[NotLanded] Implement the fetching algorithm of the Web Manifest.

Source/core/testing/URLTestHelpers.cpp

Index: Source/core/testing/URLTestHelpers.cpp
diff --git a/Source/core/testing/URLTestHelpers.cpp b/Source/core/testing/URLTestHelpers.cpp
index bb67648dbf476ac0a8dd1375adb93c43c19ca839..1a0f261d8b1eb85092806f31d44bfd7c6dfd4a4a 100644
--- a/Source/core/testing/URLTestHelpers.cpp
+++ b/Source/core/testing/URLTestHelpers.cpp
@@ -53,8 +53,7 @@ void registerMockedURLLoad(const WebURL& fullURL, const WebString& fileName, con
 
 void registerMockedURLLoad(const WebURL& fullURL, const WebString& fileName, const WebString& relativeBaseDirectory, const WebString& mimeType)
 {
-    WebURLResponse response;
-    response.initialize();
+    WebURLResponse response(fullURL);
     response.setMIMEType(mimeType);
     response.setHTTPStatusCode(200);