Adding a router class to handle messages that expect responses.

mojo/bindings/java/src/org/chromium/mojo/bindings/MessageReceiverWithResponder.java

Index: mojo/bindings/java/src/org/chromium/mojo/bindings/MessageReceiverWithResponder.java
diff --git a/mojo/bindings/java/src/org/chromium/mojo/bindings/MessageReceiverWithResponder.java b/mojo/bindings/java/src/org/chromium/mojo/bindings/MessageReceiverWithResponder.java
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index 0000000000000000000000000000000000000000..afefad44a056b836957ffba7ad143d8a76002f57
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+++ b/mojo/bindings/java/src/org/chromium/mojo/bindings/MessageReceiverWithResponder.java
@@ -0,0 +1,21 @@
+// 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.
+
+package org.chromium.mojo.bindings;
+
+/**
+ * A {@link MessageReceiver} that can also handle the handle the response message generated from the
+ * given message.
+ */
+public interface MessageReceiverWithResponder extends MessageReceiver {
+
+    /**
+     * A variant on {@link #accept(MessageWithHeader)} that registers a {@link MessageReceiver}
+     * (known as the responder) to handle the response message generated from the given message. The
+     * responder's {@link #accept(MessageWithHeader)} method may be called as part of the call to
+     * {@link #acceptWithResponder(MessageWithHeader, MessageReceiver)}, or some time after its
+     * return.
+     */
+    boolean acceptWithResponder(MessageWithHeader message, MessageReceiver responder);
+}