Control zero suggest with a pref, not a switch.

chrome/browser/resources/instant/instant.js

 // Copyright (c) 2012 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.
 
 // Redefine '$' here rather than including 'cr.js', since this is
 // the only function needed.  This allows this file to be loaded
 // in a browser directly for layout and some testing purposes.
 var $ = function(id) { return document.getElementById(id); };
 
 /**
  * WebUI for configuring instant.* preference values used by
  * Chrome's instant search system.
  */
 var instantConfig = (function() {
   'use strict';
 
   /** List of fields used to dynamically build form. **/
   var FIELDS = [
     {
       key: 'instant.animation_scale_factor',
       label: 'Slow down animations by a factor of',
+      type: 'float',
       units: 'no units, range 1 to 10',
       default: 1
+    },
+    {
+      key: 'instant.experimental_zero_suggest_url_prefix',
+      label: 'Prefix URL for the (experimental) ZeroSuggest provider',
+      type: 'string',
+      units: '',
+      default: ''
     }
   ];
 
   /**
    * Returns a DOM element of the given type and class name.
    */
   function createElementWithClass(elementType, className) {
     var element = document.createElement(elementType);
     element.className = className;
     return element;
@@ skipping 11 matching lines @@
 
       var row = createElementWithClass('div', 'row');
       row.id = '';
 
       var label = createElementWithClass('label', 'row-label');
       label.setAttribute('for', field.key);
       label.textContent = field.label;
       row.appendChild(label);
 
       var input = createElementWithClass('input', 'row-input');
-      input.type = 'number';
-      input.size = 3;
       input.id = field.key;
-      input.min = field.min || 0;
       input.title = "Default Value: " + field.default;
-      if (field.max) input.max = field.max;
-      if (field.step) input.step = field.step;
+      if (field.type == 'float') {
+        input.size = 3;
+        input.type = 'number';
+        input.min = field.min || 0;
+        if (field.max) input.max = field.max;
+        if (field.step) input.step = field.step;
+      } else {
+        input.size = 40;
+      }
       row.appendChild(input);
 
       var units = createElementWithClass('div', 'row-units');
       if (field.units)
         units.innerHTML = field.units;
       row.appendChild(units);
 
       $('instant-form').appendChild(row);
     }
   }
@@ skipping 28 matching lines @@
   function getPreferenceValueResult(prefName, value) {
     $(prefName).value = value;
   }
 
   /**
    * Set a preference setting's value.
    * @param {string} prefName The name of the preference value being set.
    * @param {value} value The value to be associated with prefName.
    */
   function setPreferenceValue(prefName, value) {
-    chrome.send(
-        'setPreferenceValue',
-        [prefName, parseFloat(value)]);
+    chrome.send('setPreferenceValue', [prefName, value]);
   }
 
   /**
    * Handle processing of "Reset" button.
    * Causes off form values to be updated based on current preference values.
    */
   function onReset() {
     for (var i = 0; i < FIELDS.length; i++) {
       var field = FIELDS[i];
       $(field.key).value = field.default;
       setPreferenceValue(field.key, field.default);
     }
     return false;
   }
 
   /**
    * Saves data back into Chrome preferences.
    */
   function onSave() {
     for (var i = 0; i < FIELDS.length; i++) {
       var field = FIELDS[i];
-      setPreferenceValue(field.key, $(field.key).value);
+      var value = $(field.key).value;
+      setPreferenceValue(
+          field.key, (field.type == 'float') ? parseFloat(value) : value);
     }
     return false;
   }
 
 
   function loadForm() {
     for (var i = 0; i < FIELDS.length; i++)
       getPreferenceValue(FIELDS[i].key);
   }
 
   /**
    * Build and initialize the configuration form.
    */
   function initialize() {
     buildForm();
     loadForm();
     initForm();
 
     $('reset-button').onclick = onReset.bind(this);
     $('save-button').onclick = onSave.bind(this);
   }
 
   return {
     initialize: initialize,
     getPreferenceValueResult: getPreferenceValueResult
   };
 })();
 
 document.addEventListener('DOMContentLoaded', instantConfig.initialize);