[Android NTP] Cache number of items under child nodes

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/InnerNode.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/InnerNode.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/InnerNode.java
index 2b9d1f322f1f785e1f0f4a2e1234d0692bc20f35..93df5b6de4ca8e16a767258f88a450cd9a95ff7e 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/InnerNode.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/InnerNode.java
@@ -57,7 +57,7 @@ public class InnerNode extends ChildNode implements NodeParent {
     }
 
     @Override
-    public int getItemCount() {
+    protected int getItemCountForDebugging() {
         int numItems = 0;
         for (TreeNode child : mChildren) {
             numItems += child.getItemCount();
@@ -137,12 +137,13 @@ public class InnerNode extends ChildNode implements NodeParent {
      */
     protected void addChildren(TreeNode... children) {
         int initialCount = getItemCount();
+        int addedCount = 0;
         for (TreeNode child : children) {
             mChildren.add(child);
             child.setParent(this);
+            addedCount += child.getItemCount();
         }
 
-        int addedCount = getItemCount() - initialCount;
         if (addedCount > 0) notifyItemRangeInserted(initialCount, addedCount);
     }