[Offline pages] Detecting missing offline copy

chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarksModel.java

 // Copyright 2015 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.chrome.browser.enhancedbookmarks;
 
 import android.content.Context;
 
 import org.chromium.base.ObserverList;
 import org.chromium.base.VisibleForTesting;
@@ skipping 87 matching lines @@
             }
         }
     }
 
     /**
      * Clean up all the bridges. This must be called after done using this class.
      */
     @Override
     public void destroy() {
         if (mOfflinePageBridge != null) {
+            mOfflinePageBridge.removeObserver(mOfflinePageModelObserver);
             mOfflinePageBridge.destroy();
             mOfflinePageBridge = null;
         }
 
         super.destroy();
     }
 
     @Override
     public boolean isBookmarkModelLoaded() {
         return super.isBookmarkModelLoaded()
@@ skipping 158 matching lines @@
         return bookmarkIds;
     }
 
     /**
      * @return Offline page bridge.
      */
     public OfflinePageBridge getOfflinePageBridge() {
         return mOfflinePageBridge;
     }
 }