[Android] Allow setting recently visited search engines as default search engine

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 102 matching lines @@
     <dimen name="overlay_panel_text_size">18sp</dimen>
 
     <!-- Password generation popup dimensions -->
     <dimen name="password_generation_divider_height">1dp</dimen>
     <dimen name="password_generation_text_size">14sp</dimen>
     <dimen name="password_generation_horizontal_margin">10dp</dimen>
     <dimen name="password_generation_text_vertical_margin">12dp</dimen>
 
     <!-- Preferences dimensions -->
     <dimen name="pref_autofill_touch_target_padding">15dp</dimen>
+    
+    <!-- Search engine preference dimensions -->
+    <dimen name="search_engine_list_margin_top">6dp</dimen>
 
     <!-- Site Settings dimensions -->
     <dimen name="site_setttings_icon_padding">4.6dp</dimen>
 
     <!-- Minimum height/width for a touchable item -->
     <dimen name="min_touch_target_size">48dp</dimen>
 
     <!-- Data Saver -->
     <dimen name="data_usage_chart_height">252dp</dimen>
     <dimen name="data_reduction_promo_screen_width">330dp</dimen>
@@ skipping 232 matching lines @@
     <dimen name="pref_autofill_field_horizontal_padding">4dp</dimen>
     <dimen name="pref_autofill_field_top_margin">8dp</dimen>
 
     <!-- Dialog dimensions.
          https://www.google.com/design/spec/components/dialogs.html#dialogs-simple-dialogs -->
     <dimen name="dialog_width_unit">56dp</dimen>  <!-- MD dialog widths are multiples of this. -->
 
     <!-- Downloads dimensions. -->
     <dimen name="downloads_item_icon_size">48dp</dimen>
 </resources>