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

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.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.Set;
 
 /**
  * A tree interface to allow the New Tab Page RecyclerView to delegate to other components.
  */
 public interface TreeNode {
     /**
      * Sets the parent of this node. This method should be called at most once. Before the parent
      * has been set, the node will not send any notifications about changes to its subtree.
@@ skipping 26 matching lines @@
 
     /**
      * Display the data at {@code position} under this subtree.
      * @param holder The view holder that should be updated.
      * @param position The position of the item under this subtree.
      * @see android.support.v7.widget.RecyclerView.Adapter#onBindViewHolder
      */
     void onBindViewHolder(NewTabPageViewHolder holder, int position);
 
     /**
-     * @param position The position to query.
-     * @return The article at {@code position} under this subtree, or null if the item is not
-     * an article.
-     */
-    SnippetArticle getSuggestionAt(int position);
-
-    /**
      * @param position the position of an item to be dismissed.
      * @return the set of item positions that should be dismissed simultaneously when dismissing the
      *         item at the given {@code position} (including the position itself), or an empty set
      *         if the item can't be dismissed.
      * @see NewTabPageAdapter#getItemDismissalGroup
      */
     Set<Integer> getItemDismissalGroup(int position);
 
     /**
      * Dismiss the item at the given {@code position}.
      * @param position The position of the item to be dismissed.
      * @param itemRemovedCallback Should be called with the title of the dismissed item, to announce
      * it for accessibility purposes.
      * @see NewTabPageAdapter#dismissItem
      */
-    public void dismissItem(int position, Callback<String> itemRemovedCallback);
+    void dismissItem(int position, Callback<String> itemRemovedCallback);
+
+    /**
+     * Iterates over all items under this subtree and visits them with the given
+     * {@link NodeVisitor}.
+     * @param visitor The {@link NodeVisitor} with which to visit all items under this subtree.
+     */
+    void visitItems(NodeVisitor visitor);
 }