[Android NTP] Move suggestion sections into a separate node.

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 android.support.annotation.CallSuper;
+
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
 
 /**
  * A tree interface to allow the New Tab Page RecyclerView to delegate to other components.
  */
 interface TreeNode {
     /**
+     * Initialize the node (and any children underneath it). This method should be called after the
+     * node has been added to the tree, i.e. when it is in the list of its parent's children.
+     * The node may notify its parent about changes that happen during initialization.
+     */
+    @CallSuper
+    void init();
+
+    /**
+     * Returns the number of items under this subtree. This method may be called
+     * before initialization.
+     *
      * @return The number of items under this subtree.
      * @see android.support.v7.widget.RecyclerView.Adapter#getItemCount()
      */
     int getItemCount();
 
     /**
      * @param position The position to query
      * @return The view type of the item at {@code position} under this subtree.
      * @see android.support.v7.widget.RecyclerView.Adapter#getItemViewType
      */
@@ skipping 20 matching lines @@
      * one. For example, if we want to dismiss a status card that has a More button attached, the
      * button is the card's dismiss sibling. This function returns the adapter position delta to
      * apply to get to the sibling from the provided item. For the previous example, it would return
      * {@code +1}, as the button comes right after the status card.
      *
      * @return a position delta to apply to the position of the provided item to get the adapter
      * position of the item to animate. Returns {@code 0} if there is no dismiss sibling.
      */
     int getDismissSiblingPosDelta(int position);
 }