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

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.java
index 6c76fcb6c7be149c5e4e62f37022bf1ae8c3c68e..75997a493b5d2cba0d22cfc559b89de60a92aaee 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.java
@@ -4,6 +4,8 @@
 
 package org.chromium.chrome.browser.ntp.cards;
 
+import android.support.annotation.CallSuper;
+
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
 
 /**
@@ -11,6 +13,17 @@ import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
  */
 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()
      */