Introduce a field trial for Instant.

chrome/browser/resources/options/browser_options.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() {
   const OptionsPage = options.OptionsPage;
   const ArrayDataModel = cr.ui.ArrayDataModel;
 
   //
   // BrowserOptions class
@@ skipping 65 matching lines @@
           if (self.instantConfirmDialogShown_)
             chrome.send('enableInstant');
           else
             OptionsPage.navigateToPage('instantConfirm');
         } else {
           chrome.send('disableInstant');
         }
         return true;
       };
 
+      $('instantFieldTrialCheckbox').addEventListener('change',
+          function(event) {
+            this.checked = true;
+            chrome.send('disableInstant');
+          });
+
       Preferences.getInstance().addEventListener('instant.confirm_dialog_shown',
           this.onInstantConfirmDialogShownChanged_.bind(this));
 
+      Preferences.getInstance().addEventListener('instant.enabled',
+          this.onInstantEnabledChanged_.bind(this));
+
       var homepageField = $('homepageURL');
       $('homepageUseNTPButton').onchange =
           this.handleHomepageUseNTPButtonChange_.bind(this);
       $('homepageUseURLButton').onchange =
           this.handleHomepageUseURLButtonChange_.bind(this);
       var homepageChangeHandler = this.handleHomepageURLChange_.bind(this);
       homepageField.addEventListener('change', homepageChangeHandler);
       homepageField.addEventListener('input', homepageChangeHandler);
       homepageField.addEventListener('focus', function(event) {
         self.autocompleteList_.attachToInput(homepageField);
@@ skipping 63 matching lines @@
      * Called when the value of the instant.confirm_dialog_shown preference
      * changes. Cache this value.
      * @param {Event} event Change event.
      * @private
      */
     onInstantConfirmDialogShownChanged_: function(event) {
       this.instantConfirmDialogShown_ = event.value['value'];
     },
 
     /**
+     * Called when the value of the instant.enabled preference changes. Request
+     * the state of the Instant field trial experiment.
+     * @param {Event} event Change event.
+     * @private
+     */
+    onInstantEnabledChanged_: function(event) {
+      chrome.send('getInstantFieldTrialStatus');
+    },
+
+    /**
+     * Called to set the Instant field trial status.
+     * @param {boolean} enabled If true, the experiment is enabled.
+     * @private
+     */
+    setInstantFieldTrialStatus_: function(enabled) {
+      $('instantEnabledCheckbox').hidden = enabled;
+      $('instantFieldTrialCheckbox').hidden = !enabled;
+    },
+
+    /**
      * Update the Default Browsers section based on the current state.
      * @param {string} statusString Description of the current default state.
      * @param {boolean} isDefault Whether or not the browser is currently
      *     default.
      * @param {boolean} canBeDefault Whether or not the browser can be default.
      * @private
      */
     updateDefaultBrowserState_: function(statusString, isDefault,
                                          canBeDefault) {
       var label = $('defaultBrowserState');
@@ skipping 300 matching lines @@
   };
 
   BrowserOptions.updateStartupPages = function(pages) {
     BrowserOptions.getInstance().updateStartupPages_(pages);
   };
 
   BrowserOptions.updateAutocompleteSuggestions = function(suggestions) {
     BrowserOptions.getInstance().updateAutocompleteSuggestions_(suggestions);
   };
 
+  BrowserOptions.setInstantFieldTrialStatus = function(enabled) {
+    BrowserOptions.getInstance().setInstantFieldTrialStatus_(enabled);
+  };
+
   // Export
   return {
     BrowserOptions: BrowserOptions
   };
 
 });