Update on Issue 8118003.

chrome/browser/resources/options/font_settings.js

 // Copyright (c) 2011 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.
 
 cr.define('options', function() {
 
   var OptionsPage = options.OptionsPage;
 
   /**
+   * This is the absolute difference maintained between standard and
+   * fixed-width font sizes. Refer http://crbug.com/91922.
+   */
+  const SIZE_DIFFERENCE_FIXED_STANDARD = 3;
+
+  /**
    * FontSettings class
    * Encapsulated handling of the 'Fonts and Encoding' page.
    * @class
    */
   function FontSettings() {
     OptionsPage.call(this,
                      'fonts',
                      templateData.fontSettingsPageTabTitle,
                      'font-settings');
   }
 
   cr.addSingletonGetter(FontSettings);
 
   FontSettings.prototype = {
     __proto__: OptionsPage.prototype,
 
     /**
      * Initialize the page.
      */
     initializePage: function() {
       OptionsPage.prototype.initializePage.call(this);
 
       var standardFontRange = $('standard-font-size');
       standardFontRange.valueMap = [9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20,
           22, 24, 26, 28, 30, 32, 34, 36, 40, 44, 48, 56, 64, 72];
       standardFontRange.continuous = false;
       standardFontRange.notifyChange = this.standardRangeChanged_.bind(this);
+      standardFontRange.notifyPrefChange =
+          this.standardFontSizeChanged_.bind(this);
 
       var minimumFontRange = $('minimum-font-size');
       minimumFontRange.valueMap = [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
           18, 20, 22, 24];
       minimumFontRange.continuous = false;
       minimumFontRange.notifyChange = this.minimumRangeChanged_.bind(this);
       minimumFontRange.notifyPrefChange =
           this.minimumFontSizeChanged_.bind(this);
 
       var placeholder = localStrings.getString('fontSettingsPlaceholder');
@@ skipping 32 matching lines @@
       this.setUpFontSample_(fontSampleEl, value, fontSampleEl.style.fontFamily,
                             true);
 
       fontSampleEl = $('serif-font-sample');
       this.setUpFontSample_(fontSampleEl, value, fontSampleEl.style.fontFamily,
                             true);
 
       fontSampleEl = $('sans-serif-font-sample');
       this.setUpFontSample_(fontSampleEl, value, fontSampleEl.style.fontFamily,
                             true);
+
+      fontSampleEl = $('fixed-font-sample');
+      this.setUpFontSample_(fontSampleEl,
+                            value - SIZE_DIFFERENCE_FIXED_STANDARD,
+                            fontSampleEl.style.fontFamily, false);
     },
 
     /**
+     * Sets the 'default_fixed_font_size' preference when the standard font
+     * size has been changed by the user.
+     * @param {Element} el The slider input element.
+     * @param {number} value The mapped value that has been saved.
+     * @private
+     */
+    standardFontSizeChanged_: function(el, value) {
+      Preferences.setIntegerPref('webkit.webprefs.default_fixed_font_size',
+                                 value - SIZE_DIFFERENCE_FIXED_STANDARD, '');
+    },
+
+    /**
      * Called as the user changes the miniumum font size.  This allows for
      * reflecting the change in the UI before the preference has been changed.
      * @param {Element} el The slider input element.
      * @param {number} value The mapped value currently set by the slider.
      * @private
      */
     minimumRangeChanged_: function(el, value) {
       var fontSampleEl = $('minimum-font-sample');
       this.setUpFontSample_(fontSampleEl, value, fontSampleEl.style.fontFamily,
                             true);
@@ skipping 98 matching lines @@
     FontSettings.getInstance().setUpFontSample_($('minimum-font-sample'), size,
                                                 null, true);
   };
 
   // Export
   return {
     FontSettings: FontSettings
   };
 });