Introduce a field trial for Instant.

chrome/browser/resources/options/browser_options.js

Index: chrome/browser/resources/options/browser_options.js
diff --git a/chrome/browser/resources/options/browser_options.js b/chrome/browser/resources/options/browser_options.js
index ffd838e4a2c7fa0d24f777617a75f8a37c5b43be..e8b46fb4168c9f0734fd2230780f089c326c5692 100644
--- a/chrome/browser/resources/options/browser_options.js
+++ b/chrome/browser/resources/options/browser_options.js
@@ -83,9 +83,18 @@ cr.define('options', function() {
         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);
@@ -169,6 +178,26 @@ cr.define('options', function() {
     },
 
     /**
+     * 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
@@ -489,6 +518,10 @@ cr.define('options', function() {
     BrowserOptions.getInstance().updateAutocompleteSuggestions_(suggestions);
   };
 
+  BrowserOptions.setInstantFieldTrialStatus = function(enabled) {
+    BrowserOptions.getInstance().setInstantFieldTrialStatus_(enabled);
+  };
+
   // Export
   return {
     BrowserOptions: BrowserOptions