Implement clearListener() method for PositionObserver to clear all registered listeners when Con

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

 // Copyright 2013 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;
 
 /**
  * Used to register listeners that can be notified of changes to the position of a view.
  */
 public interface PositionObserver {
@@ skipping 16 matching lines @@
 
     /**
      * Register a listener to be called when the position of the underlying view changes.
      */
     void addListener(Listener listener);
 
     /**
      * Remove a previously installed listener.
      */
     void removeListener(Listener listener);
+
+    /**
+     * Clears registerned listener(s).
+     */
+    void clearListener();
 }