Add a content API to create a message channel.

content/public/android/java/src/org/chromium/content/browser/MessageChannel.java

+// 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.content.browser;
+
+/**
+ * Represents the MessageChannel object. Inspired by
+ * http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#message-channels
+ */
+class MessageChannel {
+    private int mPort1;
+    private int mPort2;
+
+    MessageChannel(int port1, int port2) {
+        mPort1 = port1;
+        mPort2 = port2;
+    }
+
+    int port1() { return mPort1; }
+    int port2() { return mPort2; }
+}