SheriffOMatic: Add ct-popout-iframe and switch test output iframes to use it.

Tools/GardeningServer/ui/test/ct-test-output-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-test-output.html">
 
 <script>
 (function () {
@@ skipping 32 matching lines @@
   describe('text', function() {
     before(function() {
       resultType = results.kTextType;
       url = 'http://domain.com/dummy-expected';
     });
 
     it('text', function() {
       assert.lengthOf(output.shadowRoot.querySelectorAll('img'), 0);
       assert.lengthOf(output.shadowRoot.querySelectorAll('audio'), 0);
 
-      var iframes = output.shadowRoot.querySelectorAll('iframe');
+      var iframes = output.shadowRoot.querySelectorAll('ct-popout-iframe');
       assert.lengthOf(iframes, 1);
       assert.equal(iframes[0].src, url);
     });
   });
 
   describe('audio', function() {
     before(function() {
       resultType = results.kAudioType;
       url = 'http://domain.com/dummy-expected';
     });
@@ skipping 30 matching lines @@
     it('no output', function() {
       assert.lengthOf(output.shadowRoot.querySelectorAll('iframe'), 0);
       assert.lengthOf(output.shadowRoot.querySelectorAll('audio'), 0);
       assert.lengthOf(output.shadowRoot.querySelectorAll('img'), 0);
     });
   });
 });
 
 })();
 </script>