selection: Align collapse-NN.html and extend-NN.html to the latest draft.

third_party/WebKit/LayoutTests/external/wpt/selection/common.js

 "use strict";
 // TODO: iframes, contenteditable/designMode
 
 // Everything is done in functions in this test harness, so we have to declare
 // all the variables before use to make sure they can be reused.
 var selection;
 var testDiv, paras, detachedDiv, detachedPara1, detachedPara2,
     foreignDoc, foreignPara1, foreignPara2, xmlDoc, xmlElement,
     detachedXmlElement, detachedTextNode, foreignTextNode,
     detachedForeignTextNode, xmlTextNode, detachedXmlTextNode,
@@ skipping 940 matching lines @@
  * direction backwards.  Uses extend, so it will throw in IE.  Accepts an empty
  * array for endpoints, in which case the selection will just be emptied.
  */
 function setSelectionBackwards(endpoints) {
     selection.removeAllRanges();
     if (endpoints.length) {
         selection.collapse(endpoints[2], endpoints[3]);
         selection.extend(endpoints[0], endpoints[1]);
     }
 }
+
+/**
+ * Verify that the specified func doesn't change the selection.
+ * This function should be used in testharness tests.
+ */
+function assertSelectionNoChange(func) {
+    var originalCount = getSelection().rangeCount;
+    var originalRange = originalCount == 0 ? null : selection.getRangeAt(0);
+
+    func();
+
+    assert_equals(selection.rangeCount, originalCount,
+        "The operation should not add Range");
+    if (originalCount < 1)
+        return;
+    assert_equals(selection.getRangeAt(0), originalRange,
+         "The operation should not replace a registered Range");
+}
+