Unify NewTabPageItem and ItemGroup into a single tree-structured interface.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/StatusItem.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/StatusItem.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/StatusItem.java
index 9285ff97fbc3eef8551392785c31badf0959c34a..f4821b6ff5fba12a8c51e4efeefcf474cbdc9b5b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/StatusItem.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/StatusItem.java
@@ -13,7 +13,7 @@ import org.chromium.chrome.R;
  * Card that is shown when the user needs to be made aware of some information about their
  * configuration that affects the NTP suggestions.
  */
-public abstract class StatusItem implements NewTabPageItem, StatusCardViewHolder.DataSource {
+public abstract class StatusItem extends Leaf implements StatusCardViewHolder.DataSource {
     public static StatusItem createNoSuggestionsItem(SuggestionsCategoryInfo categoryInfo) {
         return new NoSuggestionsItem(categoryInfo);
     }
@@ -50,12 +50,13 @@ public abstract class StatusItem implements NewTabPageItem, StatusCardViewHolder
     }
 
     @Override
-    public int getType() {
-        return NewTabPageItem.VIEW_TYPE_STATUS;
+    @ItemViewType
+    protected int getItemViewType() {
+        return ItemViewType.VIEW_TYPE_STATUS;
     }
 
     @Override
-    public void onBindViewHolder(NewTabPageViewHolder holder) {
+    protected void onBindViewHolder(NewTabPageViewHolder holder) {
         assert holder instanceof StatusCardViewHolder;
         ((StatusCardViewHolder) holder).onBindViewHolder(this);
     }