Mojo C++ bindings: remove the lock in MultiplexRouter if it only serves a single interface.

mojo/public/cpp/bindings/associated_interface_ptr.h

 // Copyright 2015 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.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_ASSOCIATED_INTERFACE_PTR_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_ASSOCIATED_INTERFACE_PTR_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 213 matching lines @@
 
   ptr->Bind(std::move(ptr_info), std::move(runner));
   return request;
 }
 
 // Creates an associated interface proxy which casts its messages into the void.
 template <typename Interface>
 void GetDummyProxyForTesting(AssociatedInterfacePtr<Interface>* proxy) {
   MessagePipe pipe;
   scoped_refptr<internal::MultiplexRouter> router =
-      new internal::MultiplexRouter(false, std::move(pipe.handle0),
-                                    base::ThreadTaskRunnerHandle::Get());
+      new internal::MultiplexRouter(std::move(pipe.handle0),
+                                    internal::MultiplexRouter::MULTI_INTERFACE,
+                                    false, base::ThreadTaskRunnerHandle::Get());
   std::unique_ptr<AssociatedGroup> group = router->CreateAssociatedGroup();
   GetProxy(proxy, group.get());
 }
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_ASSOCIATED_INTERFACE_PTR_H_