Add new NTP layout with snippet cards and hide it behind a flag

chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/HeaderListItem.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/HeaderListItem.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/HeaderListItem.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/HeaderListItem.java
new file mode 100644
index 0000000000000000000000000000000000000000..13539d6dbd876ee7b72063152c910ecbb57d153a
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/HeaderListItem.java
@@ -0,0 +1,47 @@
+// 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.v2;
+
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.ntp.NewTabPageViewHolder;
+
+/**
+ * Represents the data for a header of a group of snippets
+ */
+public class HeaderListItem implements NewTabPageListItem {
+    /**
+     * A class that represents the view for a header of a group of card snippets.
+     */
+    public static class ViewHolder extends NewTabPageViewHolder {

[newt (away), 2016/03/30 19:03:51]

This looks identical to SnippetHeaderViewHolder. Are they both needed / is one
unused?

[dgn, 2016/03/31 00:46:45]

made NTPViewHolder concrete and removed those two, as they don't bring anything
special currently.

+        public ViewHolder(View view) {
+            super(view);
+        }
+
+        /**
+         * Creates the TextView object for displaying the header for a group of snippets

[newt (away), 2016/03/30 19:03:50]

I'd replace "TextView" with "View", since "TextView" is an implementation detail
(plus, the layout could change in the future).

[dgn, 2016/03/31 00:46:45]

Done.

+         *
+         * @param parent The parent view for the header
+         * @return a TextView object for displaying a header for a group of snippets
+         */
+        public static View createView(ViewGroup parent) {
+            return LayoutInflater.from(parent.getContext())
+                    .inflate(R.layout.new_tab_page_snippets_header, parent, false);
+        }
+
+        @Override
+        public void onBindViewHolder(NewTabPageListItem snippetItem) {}
+    }
+
+    public HeaderListItem() {}

[newt (away), 2016/03/30 19:03:50]

not needed

[dgn, 2016/03/31 00:46:45]

Done.

+
+    @Override
+    public int getType() {
+        return NewTabPageListItem.VIEW_TYPE_HEADER;
+    }
+}