Issue #1543 - Align <img> with no src to the updated spec.

accessible/tests/mochitest/tree/test_invalid_img.xhtml

@@ -20,8 +20,8 @@
       document.getElementsByTagName("img")[0].firstChild.data = "2";
 
       var accTree = {
-        role: ROLE_TEXT,
-        children: [ { role: ROLE_TEXT_LEAF } ]
+        role: ROLE_GRAPHIC,
+        children: []
       };
       testAccessibleTree("the_img", accTree);
       SimpleTest.finish();