[Android NTP] Move more of the dismissal logic into the tree.

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 c08736cf9f1899e088456d66660f528101880afc..7a13f6f5eb3e019a21e092e77ea758ad399be93c 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
@@ -7,14 +7,16 @@ 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.
  */
 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.
+     * 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.
+     * @param parent the parent of this node.
      */
     void setParent(NodeParent parent);
 
@@ -51,22 +53,20 @@ interface TreeNode {
     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);
-
-    /**
-     * The dismiss sibling is an item that should be dismissed at the same time as the provided
-     * 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);
 }