Add support for mocking failed loads to WebURLLoaderMock.

webkit/support/webkit_support.cc

Index: webkit/support/webkit_support.cc
===================================================================
--- webkit/support/webkit_support.cc	(revision 148351)
+++ webkit/support/webkit_support.cc	(working copy)
@@ -487,6 +487,13 @@
       RegisterURL(url, response, file_path);
 }
 
+void RegisterMockedErrorURL(const WebKit::WebURL& url,
+                            const WebKit::WebURLResponse& response,
+                            const WebKit::WebURLError& error) {
+  test_environment->webkit_platform_support()->url_loader_factory()->
+      RegisterErrorURL(url, response, error);
+}
+
 void UnregisterMockedURL(const WebKit::WebURL& url) {
   test_environment->webkit_platform_support()->url_loader_factory()->
     UnregisterURL(url);