Bug 1509293: Add test case r=djvj

Differential Revision: https://phabricator.services.mozilla.com/D13436

--HG--
extra : moz-landing-system : lando

js/src/jit-test/tests/cacheir/bug1509293.js

@@ -0,0 +1,2 @@
+var summary = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';
+Array.prototype.push([...summary]);