[mojo] Implement pipe fusion API

mojo/public/interfaces/bindings/tests/sample_interfaces.mojom

 // 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.
 
 [JavaPackage="org.chromium.mojo.bindings.test.mojom.sample",
  JavaConstantsClassName="InterfaceConstants",
  Foo = "hello world"]
 module sample;
 
 const uint64 kLong = 4405;
 
 enum Enum {
   VALUE
 };
 
+interface PingTest {
+  Ping() => ();
+};
+
 interface Provider {
   EchoString(string a) => (string a);
   EchoStrings(string a, string b) => (string a, string b);
   EchoMessagePipeHandle(handle<message_pipe> a) => (handle<message_pipe> a);
   EchoEnum(Enum a) => (Enum a);
   EchoInt(int32 a) => (int32 a);
 };
 
 interface IntegerAccessor {
   GetInteger() => (int64 data, [MinVersion=2] Enum type);
   [MinVersion=1]
   SetInteger(int64 data, [MinVersion=3] Enum type);
 };