Added support for layout render tests. These use expected values for the text render output from Du…

utils/testrunner/utils.dart

Index: utils/testrunner/utils.dart
===================================================================
--- utils/testrunner/utils.dart	(revision 11963)
+++ utils/testrunner/utils.dart	(working copy)
@@ -100,3 +100,15 @@
   var f = new File(fname);
   f.deleteSync();
 }
+
+/** Get the name of the layout render file for a test. */
+String layoutFileName(String testname) =>
+  testname.replaceAll(new RegExp('\.dart\$'), '.render');
+
+/** Check if a test is a layout render test. renders.
+ */
+bool isLayoutRenderTest(String testname) {
+  var layoutname = layoutFileName(testname);
+  var f = new File(layoutname);
+  return f.existsSync();
+}