Replace assets for avatar placeholder on Android

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 317 matching lines @@
     <dimen name="snippets_article_header_height">40dp</dimen>
     <dimen name="snippets_publisher_margin_top_with_article_snippet">16dp</dimen>
     <dimen name="snippets_publisher_margin_top_without_article_snippet">8dp</dimen>
     <!-- This is in sp because we want the icon to scale with the TextView it sits alongside. -->
     <dimen name="snippets_offline_icon_size">18sp</dimen>
 
     <!-- Recent tabs page -->
     <dimen name="recent_tabs_visible_separator_padding">8dp</dimen>
 
     <!-- Snackbars -->
+    <dimen name="snackbar_image_size">24dp</dimen>
     <dimen name="snackbar_min_height">48dp</dimen>
     <dimen name="snackbar_width_tablet">450dp</dimen>
     <dimen name="snackbar_margin_tablet">24dp</dimen>
 
     <!-- Bookmarks dimensions -->
     <dimen name="bookmark_item_popup_width">140dp</dimen>
     <dimen name="bookmark_folder_item_left">16dp</dimen>
     <dimen name="bookmark_minimum_dialog_size_tablet">500dp</dimen>
 
     <!-- Bookmark widget dimensions -->
@@ skipping 124 matching lines @@
     <dimen name="context_menu_header_image_min_size">56dp</dimen>
     <dimen name="context_menu_header_image_max_size">56dp</dimen>
 
     <!-- Divider Dimensions -->
     <dimen name="divider_height">1dp</dimen>
 
     <!-- Search widget dimensions -->
     <dimen name="search_activity_location_bar_margin_start">16dp</dimen>
     <dimen name="search_activity_location_bar_margin_end">8dp</dimen>
 </resources>