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

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

 // Copyright 2012 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.annotation.SuppressLint;
 import android.app.Activity;
 import android.app.SearchManager;
 import android.content.ContentResolver;
@@ skipping 778 matching lines @@
         }
         mWebContents = null;
         if (mViewAndroid != null) mViewAndroid.destroy();
         mNativeContentViewCore = 0;
         mContentSettings = null;
         mJavaScriptInterfaces.clear();
         mRetainedJavaScriptObjects.clear();
         unregisterAccessibilityContentObserver();
         mGestureStateListeners.clear();
         ScreenOrientationListener.getInstance().removeObserver(this);
+        mPositionObserver.clearListener();
     }
 
     private void unregisterAccessibilityContentObserver() {
         if (mAccessibilityScriptInjectionObserver == null) {
             return;
         }
         getContext().getContentResolver().unregisterContentObserver(
                 mAccessibilityScriptInjectionObserver);
         mAccessibilityScriptInjectionObserver = null;
     }
@@ skipping 2515 matching lines @@
 
     private native void nativeExtractSmartClipData(long nativeContentViewCoreImpl,
             int x, int y, int w, int h);
     private native void nativeSetBackgroundOpaque(long nativeContentViewCoreImpl, boolean opaque);
 
     private native void nativeResumeResponseDeferredAtStart(
             long nativeContentViewCoreImpl);
     private native void nativeSetHasPendingNavigationTransitionForTesting(
             long nativeContentViewCoreImpl);
 }