Remove remaining calls to deprecated MessageLoop methods.

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

Index: mojo/public/cpp/bindings/tests/validation_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/validation_unittest.cc b/mojo/public/cpp/bindings/tests/validation_unittest.cc
index 421cda36ed7ea89e902b71e1ade215f51494e1c2..d2543836bf802868eb2328980fea7294b500e041 100644
--- a/mojo/public/cpp/bindings/tests/validation_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/validation_unittest.cc
@@ -254,7 +254,7 @@ class ValidationIntegrationTest : public ValidationTest {
     mojo::Connector connector_;
   };
 
-  void PumpMessages() { loop_.RunUntilIdle(); }
+  void PumpMessages() { base::RunLoop().RunUntilIdle(); }
 
   TestMessageReceiver* test_message_receiver_;
   ScopedMessagePipeHandle testee_endpoint_;