Fix silly error in test a=test-only

layout/reftests/table-anonymous-boxes/277995-1.html

@@ -16,7 +16,7 @@
 
       var cell = document.createElement("span");
       cell.appendChild(document.createTextNode("More Data"));
-      cell.setAttribute("style", "cell");
+      cell.setAttribute("class", "cell");
       row.appendChild(cell);
       data.appendChild(row);
     }