Merge pull request #11000 from mozilla/greenkeeper/uglify-js-3.5.2

Update uglify-js to the latest version 🚀

package.json

@@ -20,7 +20,7 @@
     "less": "3.9.0",
     "source-map": "0.7.3",
     "timeago": "1.6.5",
-    "uglify-js": "3.5.1",
+    "uglify-js": "3.5.2",
     "underscore": "1.9.1"
   },
   "devDependencies": {}