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

content/public/android/java/src/org/chromium/content/browser/ViewPositionObserver.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;
 
 import android.view.View;
 import android.view.ViewTreeObserver;
 
 import java.util.ArrayList;
@@ skipping 81 matching lines @@
     }
 
     private void updatePosition() {
         int previousPositionX = mPosition[0];
         int previousPositionY = mPosition[1];
         mView.getLocationInWindow(mPosition);
         if (mPosition[0] != previousPositionX || mPosition[1] != previousPositionY) {
             notifyListeners();
         }
     }
+
+    /**
+     * Clears installed listener(s).
+     */
+    @Override
+    public void clearListener() {
+        mListeners.clear();
+    }
 }