[Suggestions] Remove TreeNode.getSuggestionAt() in favor of a visitor.

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/Leaf.java

 // Copyright 2016 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.ntp.cards;
 
 import org.chromium.base.Callback;
-import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
 
 import java.util.Collections;
 import java.util.Set;
 
 /**
  * A permanent leaf in the tree, i.e. a single item.
  * If the leaf is not to be a permanent member of the tree, see {@link OptionalLeaf} for an
  * implementation that will take care of hiding or showing the item.
  */
 public abstract class Leaf extends ChildNode {
@@ skipping 15 matching lines @@
         return getItemViewType();
     }
 
     @Override
     public void onBindViewHolder(NewTabPageViewHolder holder, int position) {
         if (position != 0) throw new IndexOutOfBoundsException();
         onBindViewHolder(holder);
     }
 
     @Override
-    public SnippetArticle getSuggestionAt(int position) {
-        if (position != 0) throw new IndexOutOfBoundsException();
-
-        return null;
-    }
-
-    @Override
     public Set<Integer> getItemDismissalGroup(int position) {
         return Collections.emptySet();
     }
 
     @Override
     public void dismissItem(int position, Callback<String> itemRemovedCallback) {
         assert false;
     }
 
     /**
      * Display the data for this item.
      * @param holder The view holder that should be updated.
      * @see #onBindViewHolder(NewTabPageViewHolder, int)
      * @see android.support.v7.widget.RecyclerView.Adapter#onBindViewHolder
      */
     protected abstract void onBindViewHolder(NewTabPageViewHolder holder);
 
     /**
      * @return The view type of this item.
      * @see android.support.v7.widget.RecyclerView.Adapter#getItemViewType
      */
     @ItemViewType
     protected abstract int getItemViewType();
 }