Convert track-webvtt-tc[022, 023] tests to testharness.js

third_party/WebKit/LayoutTests/media/track/track-helpers.js

 function enableAllTextTracks(textTracks) {
     for (var i = 0; i < textTracks.length; i++) {
         var track = textTracks[i];
         if (track.mode == "disabled")
             track.mode = "hidden";
     }
 }
 
 function assert_cues_equal(cues, expected) {
     assert_equals(cues.length, expected.length);
@@ skipping 20 matching lines @@
         var video = document.createElement("video");
         var trackElement = document.createElement("track");
         trackElement.src = src;
         trackElement.default = true;
         video.appendChild(trackElement);
 
         trackElement.onload = t.step_func_done(function() {
             func(trackElement.track);
         });
     }, "Check cues from " + src);
+}
+
+function assert_cue_fragment(cue, children) {
+    var fragment = createFragment(children);
+    assert_true(fragment.isEqualNode(cue.getCueAsHTML()));
+}
+
+function createFragment(children) {
+    var fragment = document.createDocumentFragment();
+    cloneChildrenToFragment(fragment, children);
+    return fragment;
+}
+
+function cloneChildrenToFragment(root, children) {
+    for (var child of children) {
+        var childElement;
+        if (child.type == "text") {
+            childElement = document.createTextNode(child.value);
+        } else {
+            childElement = document.createElement(child.type);
+            cloneChildrenToFragment(childElement, child.value);
+        }
+        root.appendChild(childElement);
+    }
 }