Remove remaining calls to deprecated MessageLoop methods.

mojo/public/cpp/bindings/tests/union_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
 #include <vector>
 
 #include "base/message_loop/message_loop.h"
@@ skipping 1192 matching lines @@
   void Echo(PodUnionPtr in, const EchoCallback& callback) override {
     callback.Run(std::move(in));
   }
 };
 
 void ExpectInt16(int16_t value, PodUnionPtr out) {
   EXPECT_EQ(value, out->get_f_int16());
 }
 
 TEST(UnionTest, UnionInInterface) {
-  base::MessageLoop run_loop;
+  base::MessageLoop message_loop;
   UnionInterfaceImpl impl;
   UnionInterfacePtr ptr;
   Binding<UnionInterface> bindings(&impl, GetProxy(&ptr));
 
   PodUnionPtr pod(PodUnion::New());
   pod->set_f_int16(16);
 
   ptr->Echo(std::move(pod), base::Bind(&ExpectInt16, 16));
-  run_loop.RunUntilIdle();
+  base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace test
 }  // namespace mojo