Add some perf tests to compare Mojo overhead.

ipc/ipc_test.mojom

 // Copyright 2016 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.
 
 module IPC.mojom;
 
 interface SimpleTestDriver {
   ExpectValue(int32 value);
 
   [Sync]
@@ skipping 10 matching lines @@
   RequestValue() => (int32 value);
 };
 
 interface PingReceiver {
   Ping() => ();
 };
 
 interface IndirectTestDriver {
   GetPingReceiver(associated PingReceiver& request);
 };
+
+interface Reflector {
+  Ping(string value) => (string value);
+  Quit();
+};