trying to add a delay to allow browsers to catch up with responsiveness test

tests/frontend/specs/responsiveness.js

@@ -78,7 +78,7 @@ describe('Responsiveness of Editor', function() {
         var end = Date.now(); // get the current time
         var delay = end - start; // get the delay as the current time minus the start time
 
-        expect(delay).to.be.below(400);
+        expect(delay).to.be.below(600);
         done();
       }, 5000);