use the userAgent() in the same loadable module as RendererWebKitPlatformSupportImpl

content/renderer/renderer_webkitplatformsupport_impl.cc

Index: content/renderer/renderer_webkitplatformsupport_impl.cc
diff --git a/content/renderer/renderer_webkitplatformsupport_impl.cc b/content/renderer/renderer_webkitplatformsupport_impl.cc
index 0d31ac5e47df8e50d6ded04f1591c31e22e600ac..2611add479528274868ebfdebdff3b7a059cbfbf 100644
--- a/content/renderer/renderer_webkitplatformsupport_impl.cc
+++ b/content/renderer/renderer_webkitplatformsupport_impl.cc
@@ -608,3 +608,9 @@ WebBlobRegistry* RendererWebKitPlatformSupportImpl::blobRegistry() {
   }
   return blob_registry_.get();
 }
+
+WebKit::WebString RendererWebKitPlatformSupportImpl::userAgent(
+    const WebKit::WebURL& url) {
+ return WebKitPlatformSupportImpl::userAgent(url);
+}
+