Fixed tests for FF difference.

TBR=sra@google.com

Change-Id: I8698294f8d4b8c63930616ff72df191b10eb9de9
Reviewed-on: https://dart-review.googlesource.com/60220
Reviewed-by: Terry Lucas <terry@google.com>
diff --git a/tests/lib_2/html/fontface_loaded_test.dart b/tests/lib_2/html/fontface_loaded_test.dart
index 15a00ec..7f2ebc5 100644
--- a/tests/lib_2/html/fontface_loaded_test.dart
+++ b/tests/lib_2/html/fontface_loaded_test.dart
@@ -55,7 +55,7 @@
         var fontFamily = fontFace.family;
         if (fontFamily.startsWith('"')) {
           // FF wraps family in quotes - remove the quotes.
-          fontFamily.substring(1, fontFamily.length - 1);
+          fontFamily = fontFamily.substring(1, fontFamily.length - 1);
         }
         expect(fontFamily, 'Ahem');
       }