Bug 1379515 - Propagate testharness functions only if we use testharn…

…ess.js. r=birtles

We are going to use SimpleTest.js in the sub window.

MozReview-Commit-ID: HAAMnY7xDNn

--HG--
extra : rebase_source : 3600376a992abf5e1e55baba99bff1a656afdaa6

dom/animation/test/testcommon.js

@@ -274,7 +274,9 @@ if (opener) {
                         "assert_class_string", "assert_throws",
                         "assert_unreached", "assert_regexp_match",
                         "promise_test", "test"]) {
-    window[funcName] = opener[funcName].bind(opener);
+    if (opener[funcName]) {
+      window[funcName] = opener[funcName].bind(opener);
+    }
   }
 
   window.EventWatcher = opener.EventWatcher;