[Sync] Add a simple UI to sync-internals to create UserEvents.

components/sync/driver/resources/chrome_sync.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.
 
 // require cr.js
 // require cr/event_target.js
 // require cr/util.js
 
 cr.define('chrome.sync', function() {
   'use strict';
@@ skipping 60 matching lines @@
 
   /**
    * Asks the browser to send us the list of registered types.  Should result
    * in an onReceivedListOfTypes event being emitted.
    */
   var requestListOfTypes = function() {
     chrome.send('requestListOfTypes');
   };
 
   /**
+   * Asks the browser if we should show the User Events tab or not.
+   */
+  var requestUserEventsVisibility = function() {
+    chrome.send('requestUserEventsVisibility');
+  };
+
+  /**
+   * Sends data to construct a user event that should be committed.

[Dan Beam, 2017/05/22 23:44:46]

can you document each @param here?

[skym, 2017/05/24 00:20:24]

Done.

+   */
+  var writeUserEvent = function(eventTimeUsec, navigationId) {
+    chrome.send('writeUserEvent', [eventTimeUsec, navigationId]);
+  };
+
+  /**
    * Counter to uniquely identify requests while they're in progress.
    * Used in the implementation of GetAllNodes.
    */
   var requestId = 0;
 
   /**
    * A map from counter values to asynchronous request callbacks.
    * Used in the implementation of GetAllNodes.
    * @type {{number: !Function}}
    */
@@ skipping 24 matching lines @@
   return {
     makeTimer: makeTimer,
     dispatchEvent: dispatchEvent,
     events: new cr.EventTarget(),
     getAllNodes: getAllNodes,
     getAllNodesCallback: getAllNodesCallback,
     registerForEvents: registerForEvents,
     registerForPerTypeCounters: registerForPerTypeCounters,
     requestUpdatedAboutInfo: requestUpdatedAboutInfo,
     requestListOfTypes: requestListOfTypes,
+    requestUserEventsVisibility: requestUserEventsVisibility,
+    writeUserEvent: writeUserEvent,
   };
 });