Generate tests for absolute layout

Summary: generate absolute layout tests. Also make sure default value for position is relative (#default div is absolutely positioned)

Reviewed By: IanChilds

Differential Revision: D3770947

fbshipit-source-id: 0327b071c0dc1aa4574ded759dcc667768b28f55

gentest/gentest.js

@@ -325,6 +325,9 @@ function pixelValue(value) {
 }
 
 function getDefaultStyleValue(style) {
+  if (style == 'position') {
+    return 'relative';
+  }
   var node = document.getElementById('default');
   return getComputedStyle(node, null).getPropertyValue(style);
 }