[MD settings] change layout of Custom Font settings

chrome/browser/resources/settings/appearance_page/appearance_fonts_page.js

 // Copyright 2015 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.
 
 (function() {
   'use strict';
 
   /**
    * This is the absolute difference maintained between standard and
    * fixed-width font sizes. http://crbug.com/91922.
@@ skipping 62 matching lines @@
         readOnly: true,
         type: Number,
         value: FONT_SIZE_RANGE_.length - 1,
       },
 
       /**
        * The interactive value of the minimum font size slider.
        * @private
        */
       immediateMinimumSizeIndex_: {
+        observer: 'immediateMinimumSizeIndexChanged_',
         type: Number,
       },
 
       /**
        * The interactive value of the font size slider.
        * @private
        */
       immediateSizeIndex_: {
+        observer: 'immediateSizeIndexChanged_',
         type: Number,
       },
 
       /**
        * Reasonable, minimum font sizes.
        * @private {!Array<number>}
        */
       minimumFontSizeRange_: {
         readOnly: true,
         type: Array,
@@ skipping 125 matching lines @@
      * @param {string} fontFamily The name of the font family use.
      * @return {string}
      * @private
      */
     computeStyle_: function(fontSize, fontFamily) {
       return 'font-size: ' + fontSize + "px; font-family: '" + fontFamily +
           "';";
     },
   });
 })();