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

chrome/android/junit/src/org/chromium/chrome/browser/ntp/cards/ContentSuggestionsTestUtils.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 org.chromium.chrome.browser.ntp.snippets.CategoryInt;
 import org.chromium.chrome.browser.ntp.snippets.ContentSuggestionsCardLayout;
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
 
@@ skipping 15 matching lines @@
         return suggestions;
     }
 
     public static SuggestionsCategoryInfo createInfo(
             @CategoryInt int category, boolean moreButton, boolean showIfEmpty) {
         return new SuggestionsCategoryInfo(
                 category, "", ContentSuggestionsCardLayout.FULL_CARD, moreButton, showIfEmpty);
     }
 
     public static SuggestionsSection createSection(
-            boolean moreButton, boolean showIfEmpty, ItemGroup.Observer observer) {
+            boolean moreButton, boolean showIfEmpty, NodeParent parent) {
         SuggestionsCategoryInfo info = createInfo(42, moreButton, showIfEmpty);
-        return new SuggestionsSection(info, observer);
+        return new SuggestionsSection(parent, info);
     }
 }