Simplify the user agent code some more since after r255534 it's not affected by the site's URL.

content/test/test_webkit_platform_support.h

Index: content/test/test_webkit_platform_support.h
===================================================================
--- content/test/test_webkit_platform_support.h	(revision 255867)
+++ content/test/test_webkit_platform_support.h	(working copy)
@@ -35,6 +35,9 @@
   virtual blink::WebIDBFactory* idbFactory();
 
   virtual blink::WebURLLoader* createURLLoader();
+  virtual blink::WebString userAgent() OVERRIDE;
+  // TODO(jam): remove this after Blink is updated
+  virtual blink::WebString userAgent(const blink::WebURL& url);
   virtual blink::WebData loadResource(const char* name);
   virtual blink::WebString queryLocalizedString(
       blink::WebLocalizedString::Name name);