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

chrome/android/java_sources.gni

Index: chrome/android/java_sources.gni
diff --git a/chrome/android/java_sources.gni b/chrome/android/java_sources.gni
index c48adbda53fc7f9077f0d70d54510cbb82f76015..51d7467ad54f823d4d3eefd97a333ac1dbb26dbe 100644
--- a/chrome/android/java_sources.gni
+++ b/chrome/android/java_sources.gni
@@ -564,25 +564,28 @@ chrome_java_sources = [
   "java/src/org/chromium/chrome/browser/ntp/cards/AllDismissedItem.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/CardViewHolder.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/CardsVariationParameters.java",
+  "java/src/org/chromium/chrome/browser/ntp/cards/ChildNode.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/DisplayStyleObserverAdapter.java",
+  "java/src/org/chromium/chrome/browser/ntp/cards/InnerNode.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/ImpressionTracker.java",
-  "java/src/org/chromium/chrome/browser/ntp/cards/ItemGroup.java",
+  "java/src/org/chromium/chrome/browser/ntp/cards/ItemViewType.java",
+  "java/src/org/chromium/chrome/browser/ntp/cards/Leaf.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/Footer.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/MarginResizer.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java",
-  "java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageItem.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageRecyclerView.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageViewHolder.java",
+  "java/src/org/chromium/chrome/browser/ntp/cards/NodeParent.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/ProgressIndicatorView.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/ProgressItem.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/ProgressViewHolder.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/SignInPromo.java",
-  "java/src/org/chromium/chrome/browser/ntp/cards/SingleItemGroup.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/SpacingItem.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/StatusCardViewHolder.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/StatusItem.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsCategoryInfo.java",
   "java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java",
+  "java/src/org/chromium/chrome/browser/ntp/cards/TreeNode.java",
   "java/src/org/chromium/chrome/browser/ntp/snippets/CategoryInt.java",
   "java/src/org/chromium/chrome/browser/ntp/snippets/FakeSuggestionsSource.java",
   "java/src/org/chromium/chrome/browser/ntp/snippets/SectionHeader.java",
@@ -1441,6 +1444,7 @@ chrome_junit_test_java_sources = [
   "junit/src/org/chromium/chrome/browser/ntp/NativePageFactoryTest.java",
   "junit/src/org/chromium/chrome/browser/ntp/TitleUtilTest.java",
   "junit/src/org/chromium/chrome/browser/ntp/cards/ContentSuggestionsTestUtils.java",
+  "junit/src/org/chromium/chrome/browser/ntp/cards/InnerNodeTest.java",
   "junit/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapterTest.java",
   "junit/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSectionTest.java",
   "junit/src/org/chromium/chrome/browser/offlinepages/BackgroundSchedulerTest.java",