[NTP Snippets] 📷 Add placeholders and start caching thumbnails

chrome/android/java/res/values/colors.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>
     <!-- Common colors -->
     <color name="default_text_color">#333</color>
     <color name="default_primary_color">#f2f2f2</color>
     <color name="light_normal_color">#5A5A5A</color>
@@ skipping 78 matching lines @@
     <color name="sad_tab_body_text_color">#646464</color>
 
     <!-- NTP Colors. Used on the bookmarks and recent tabs pages. -->
     <color name="ntp_bg">#fff</color>
     <color name="ntp_bg_incognito">#222</color>
     <color name="ntp_list_item_text">#333</color>
     <color name="ntp_list_header_text">#333</color>
     <color name="ntp_list_header_subtext">#969696</color>
     <color name="ntp_list_header_subtext_active">#7cadff</color>
     <color name="ntp_with_cards_bg">#f2f2f2</color>
+    <color name="snippets_thumnail_placeholder_bg">#f2f2f2</color>
     <color name="snippets_background_color">#fff</color>
     <color name="snippets_publisher_name_color">#646464</color>
     <color name="snippets_text_color">#646464</color>
     <color name="snippets_list_header_text_color">#646464</color>
     <color name="snippets_headline_text_color">#333333</color>
 
     <!-- Signin promo screen colors -->
     <color name="illustration_background_color">#4FC3F7</color>
 
     <!-- Contextual Search colors -->
@@ skipping 63 matching lines @@
 
     <!-- Physical Web diagnostics colors -->
     <color name="physical_web_diags_success_color">#00933b</color>
     <color name="physical_web_diags_failure_color">#f90101</color>
     <color name="physical_web_diags_indeterminate_color">#f2b50f</color>
 
     <!-- Bottom bar colors -->
     <color name="bottom_bar_shadow_color">#1d000000</color>
 
 </resources>