[MD settings] set pref to valid slider value

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 138 matching lines @@
      */
     fontSizeChanged_: function(value) {
       // TODO(michaelpg): Whitelist this pref in prefs_utils.cc so it is
       // included in the <settings-prefs> getAllPrefs call, otherwise this path
       // is invalid and nothing happens. See crbug.com/612535.
       this.set('prefs.webkit.webprefs.default_fixed_font_size.value',
           value - SIZE_DIFFERENCE_FIXED_STANDARD_);
     },
 
     /**
-     * Creates an html style value.
-     * @param {number} fontSize The font size to use.
-     * @param {string} fontFamily The name of the font family use.
-     * @return {string}
+     * Get the minimum font size, accounting for unset prefs.
+     * @return {?}
      * @private
      */
-    computeStyle_: function(fontSize, fontFamily) {
-      return 'font-size: ' + fontSize + "px; font-family: '" + fontFamily +
-          "';";
+    computeMinimumFontSize_: function() {
+      return this.get('prefs.webkit.webprefs.minimum_font_size.value') ||
+          MINIMUM_FONT_SIZE_RANGE_[0];
     },
   });
 })();