🏠 Add expand button and flag to enable it

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 436 matching lines @@
     <dimen name="bottom_nav_space_from_toolbar">96dp</dimen>
     <!-- The following two dimensions override defaults in Android's BottomNavigationView -->
     <dimen name="design_bottom_navigation_text_size">12sp</dimen>
     <dimen name="design_bottom_navigation_active_text_size">14sp</dimen>
 
     <!-- Chrome Home dimensions -->
     <dimen name="chrome_home_empty_view_top_padding">16dp</dimen>
     <dimen name="chrome_home_full_height_from_top">24dp</dimen>
     <dimen name="chrome_home_min_full_half_distance">160dp</dimen>
     <dimen name="chrome_home_progress_bar_height">4dp</dimen>
+    <dimen name="chrome_home_expand_button_extra_padding">1dp</dimen>
 
     <!-- TextBubble dimensions -->
     <dimen name="text_bubble_margin">2dp</dimen>
     <dimen name="text_bubble_corner_radius">3dp</dimen>
     <dimen name="text_bubble_menu_anchor_y_inset">-14dp</dimen>
 
     <!--  Miscellaneous dimensions -->
     <dimen name="action_bar_shadow_height">10dp</dimen>
     <dimen name="card_corner_radius">2dp</dimen>
     <dimen name="list_item_corner_radius">3dp</dimen>
     <dimen name="list_item_lateral_padding">1dp</dimen>
     <dimen name="history_default_text_margin">16dp</dimen>
 
     <!-- Context Menu Dimensions -->
     <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>