Sheriff-O-Matic: Transition more unit tests to mocha.

Tools/GardeningServer/ui/test/ct-last-updated-tests.html

 <!--
 Copyright 2014 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.
 -->
 
 <link rel="import" href="../ct-last-updated.html">
 
 <script>
 (function() {
 
-var expect = chai.expect;
+var assert = chai.assert;
 
 describe('ct-last-updated', function() {
   var builder;
 
   beforeEach(function(done) {
     builder = document.createElement('ct-last-updated');
     // Set the date to 5 minutes ago.
     builder.date = new Date(Date.now() - (5 * 60 * 1000));
     requestAnimationFrame(function() { done(); });
   });
 
   describe('default UI', function() {
     it('should have correct text', function() {
       var expected = 'Updated 5 min ago @ ' + builder.date.getHours() + ':' +
                      builder.date.getMinutes();
-      expect(builder.shadowRoot.innerHTML.trim()).to.equal(expected);
+      assert.equal(builder.shadowRoot.innerHTML.trim(), expected);
     });
   });
 });
 
 })()
 
 </script>