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

chrome/android/java/res/values/dimens.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2014 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. -->
 
 <resources>
     <!-- Connection info popup dimensions -->
     <dimen name="connection_info_padding_wide">24dp</dimen>
     <dimen name="connection_info_padding_thin">16dp</dimen>
 
@@ skipping 250 matching lines @@
     <dimen name="most_visited_min_horizontal_spacing">4dp</dimen>
     <dimen name="most_visited_max_horizontal_spacing">16dp</dimen>
     <dimen name="most_visited_tile_width">80dp</dimen>
     <dimen name="most_visited_icon_size">48dp</dimen>
     <dimen name="most_visited_offline_badge_size">24dp</dimen>
     <dimen name="ntp_logo_height">116dp</dimen>
     <dimen name="ntp_list_item_padding">16dp</dimen>
     <dimen name="ntp_list_item_min_height">48dp</dimen>
     <dimen name="ntp_list_item_text_size">16sp</dimen>
     <dimen name="ntp_shadow_height">9dp</dimen>
-    <dimen name="snippets_thumbnail_size">90dp</dimen>
-    
+    <dimen name="snippets_thumbnail_size">72dp</dimen>
+
     <!-- Interests page -->
     <dimen name="ntp_interest_item_text_size">20sp</dimen>
     <dimen name="ntp_interest_item_min_height">180dp</dimen>
     <dimen name="ntp_interest_item_image_size">120dp</dimen>
     <dimen name="ntp_interest_item_image_text_size">20sp</dimen>
 
     <!-- Recent tabs page -->
     <dimen name="recent_tabs_visible_separator_padding">8dp</dimen>
     <dimen name="recent_tabs_promo_padding">16dp</dimen>
 
@@ skipping 40 matching lines @@
 
     <!-- Account chooser dialog dimensions -->
     <dimen name="account_chooser_dialog_margin">24dp</dimen>
     <dimen name="account_chooser_dialog_item_margin">20dp</dimen>
     <dimen name="account_chooser_dialog_title_main_text_size">18sp</dimen>
     <dimen name="account_chooser_dialog_title_descriptive_text_size">16sp</dimen>
 
     <!-- Clear browsing data preferences dimensions -->
     <dimen name="clear_browsing_data_checkbox_height">56dp</dimen>
 </resources>