Rewrite scoped_ptr<T>(NULL) to use the default ctor in net/.

net/test/embedded_test_server/embedded_test_server.cc

Index: net/test/embedded_test_server/embedded_test_server.cc
diff --git a/net/test/embedded_test_server/embedded_test_server.cc b/net/test/embedded_test_server/embedded_test_server.cc
index aef1db4e3959ec5dc016aaa3d9af74491533d285..bf55539e37cad371b5d63d5bd3fe82215596777d 100644
--- a/net/test/embedded_test_server/embedded_test_server.cc
+++ b/net/test/embedded_test_server/embedded_test_server.cc
@@ -43,7 +43,7 @@ scoped_ptr<HttpResponse> HandleFileRequest(
   std::string file_contents;
   if (!file_util::ReadFileToString(
           server_root.AppendASCII(request_path), &file_contents)) {
-    return scoped_ptr<HttpResponse>(NULL);
+    return scoped_ptr<HttpResponse>();
   }
 
   scoped_ptr<BasicHttpResponse> http_response(new BasicHttpResponse);