Bug 550701 - synthesizeDragStart should not fail with |expectedDragData| = null.

r=enndeakin.

testing/mochitest/tests/SimpleTest/EventUtils.js

@@ -446,8 +446,8 @@ function synthesizeDragStart(element, expectedDragData, aWindow)
       result = null;
       if (!dataTransfer)
         throw  "no dataTransfer";
-      if (dataTransfer.mozItemCount != expectedDragData.length ||
-          expectedDragData == null)
+      if (expectedDragData == null ||
+          dataTransfer.mozItemCount != expectedDragData.length)
         throw dataTransfer;
       for (var i = 0; i < dataTransfer.mozItemCount; i++) {
         var dtTypes = dataTransfer.mozTypesAt(i);

testing/mochitest/tests/SimpleTest/tests/test_synthesizeDragStart.xul

@@ -58,16 +58,15 @@ check if nsIFile can be determined
           src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
-  <script type="application/javascript"
-          src="chrome://mochikit/content/chrome/toolkit/mozapps/downloads/tests/chrome/utils.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
   <script type="application/javascript">
   <![CDATA[
 
   /** Test for Bug 462172 synthesizeDragStart**/
-var testFile = Cc["@mozilla.org/file/directory_service;1"].
+var testFile = Components.classes["@mozilla.org/file/directory_service;1"].
                   getService(Ci.nsIProperties).get("CurWorkD", Ci.nsIFile);
+var regularDtForDrag1 = null;
 
 function doOnDragStart(aEvent)
 {
@@ -76,6 +75,7 @@ function doOnDragStart(aEvent)
     case "drag2" :
       dt.setData("text/plain", "this is text/plain");
     case "drag1" :
+      regularDtForDrag1 = dt;
       dt.setData("text/uri-list", "http://www.mozilla.org/");
       break;
     case "dragfile" :
@@ -140,6 +140,8 @@ function test() {
   isnot(result, null, "drag2 is not ordered text/uri-list then text/plain");
   result = synthesizeDragStart($("dragfile"), dragfile, window);
   is(result, null, "dragfile is nsIFile");
+  result = synthesizeDragStart($("drag1"), null, window);
+  is(result, regularDtForDrag1, "synthesizeDragStart accepts null expectedDragData");
 
   SimpleTest.finish();