Revert of Remove webrtc/libjingle/{xmllite,xmpp}

webrtc/libjingle/xmpp/module.h

+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_LIBJINGLE_XMPP_MODULE_H_
+#define WEBRTC_LIBJINGLE_XMPP_MODULE_H_
+
+#include "webrtc/libjingle/xmpp/xmppengine.h"
+
+namespace buzz {
+
+class XmppEngine;
+
+//! This is the base class for extension modules.
+//! An engine is registered with the module and the module then hooks the
+//! appropriate parts of the engine to implement that set of features.  It is
+//! important to unregister modules before destructing the engine.
+class XmppModule {
+public:
+  virtual ~XmppModule() {}
+
+  //! Register the engine with the module.  Only one engine can be associated
+  //! with a module at a time.  This method will return an error if there is
+  //! already an engine registered.
+  virtual XmppReturnStatus RegisterEngine(XmppEngine* engine) = 0;
+};
+
+}
+#endif  // WEBRTC_LIBJINGLE_XMPP_MODULE_H_