Bug 1318493 - Tell the eslint parser to use ecmaVersion 8. r=mossop

MozReview-Commit-ID: DPO9IrSxc2Q

--HG--
extra : rebase_source : fbbfd043d4bea2e61bb1baa1515a58226bdfdc75

.eslintrc.js

@@ -11,4 +11,7 @@ module.exports = {
   "env": {
     "es6": true
   },
+  "parserOptions": {
+    "ecmaVersion": 8,
+  },
 };

toolkit/components/extensions/.eslintrc.js

@@ -3,10 +3,6 @@
 module.exports = { // eslint-disable-line no-undef
   "extends": "../../.eslintrc.js",
 
-  "parserOptions": {
-    "ecmaVersion": 8,
-  },
-
   "globals": {
     "Cc": true,
     "Ci": true,