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

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageListItem.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageListItem.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageListItem.java
new file mode 100644
index 0000000000000000000000000000000000000000..d3ede56f60e33858686266f80d4ba09ef27cf8ea
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageListItem.java
@@ -0,0 +1,50 @@
+// 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 android.support.annotation.IntDef;
+import android.support.v7.widget.RecyclerView.Adapter;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** Base type for anything to add to the new tab page */
+public interface NewTabPageListItem {
+    /**
+     * View type values for the items that will be held by the NTP's RecyclerView.
+     * @see Adapter#getItemViewType(int)
+     * @see NewTabPageListItem#getType()
+     */
+    @IntDef({VIEW_TYPE_ABOVE_THE_FOLD, VIEW_TYPE_HEADER, VIEW_TYPE_SNIPPET})
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface ViewType {}
+
+    /**
+     * View type for the above the fold item
+     * @see Adapter#getItemViewType(int)
+     */
+    public static final int VIEW_TYPE_ABOVE_THE_FOLD = 1;
+
+    /**
+     * View type for card group headers
+     * @see Adapter#getItemViewType(int)
+     */
+    public static final int VIEW_TYPE_HEADER = 2;
+
+    /**
+     * View type for snippet cards
+     * @see Adapter#getItemViewType(int)
+     */
+    public static final int VIEW_TYPE_SNIPPET = 3;
+
+    /**
+      * Returns the type ({@link ViewType}) of this list item. This is so we can
+      * distinguish between different elements that are held in a single RecyclerView holder.
+      *
+      * @return the type of this list item.
+      */
+    @ViewType
+    public int getType();
+}