Bug 1553804: Follow-up: Fix another straggling chrome mochitest failure. r=bustage

MANUAL PUSH: Bustage fix.

--HG--
extra : amend_source : c8fecfa9ea6cf4867e58eba41b2092e636bbdac1

layout/xul/test/window_resizer.xul

@@ -90,7 +90,7 @@ function doTest() {
   });
 
   window.close();
-  window.opener.lastResizerTest();
+  window.arguments[0].lastResizerTest();
 }
 ]]></script>
 	<hbox id="container" flex="1">

widget/tests/test_bug596600.xul

@@ -32,9 +32,11 @@ function moveMouseTo(x, y, andThen) {
 }
 
 function openWindows() {
-  gLeftWindow = open('empty_window.xul', '_blank', 'chrome,screenX=50,screenY=50,width=200,height=200');
+  gLeftWindow = window.docShell.rootTreeItem.domWindow
+                      .open('empty_window.xul', '_blank', 'chrome,screenX=50,screenY=50,width=200,height=200');
   SimpleTest.waitForFocus(function () {
-    gRightWindow = open('empty_window.xul', '', 'chrome,screenX=300,screenY=50,width=200,height=200');
+    gRightWindow = window.docShell.rootTreeItem.domWindow
+                         .open('empty_window.xul', '', 'chrome,screenX=300,screenY=50,width=200,height=200');
     SimpleTest.waitForFocus(attachBrowserToLeftWindow, gRightWindow);
   }, gLeftWindow);
 }