Bug 1230373 - Fix an issue with eslint-plugin-mozilla not detecting the global scope properly when arrow functions are used. r=mossop

MozReview-Commit-ID: IOCM8Fjl0xQ

--HG--
extra : rebase_source : 63face219569f50bdfb00bcd7384f334ec6113c2

devtools/server/tests/mochitest/inspector_getImageData.html

@@ -10,7 +10,7 @@
     "use strict";
 
     window.onload = () => {
-      var canvas = document.querySelector("canvas"), ctx = canvas.getContext("2d");
+      let canvas = document.querySelector("canvas"), ctx = canvas.getContext("2d");
       canvas.width = 1000;
       canvas.height = 2000;
       ctx.fillStyle = "red";

tools/lint/eslint/eslint-plugin-mozilla/lib/helpers.js

@@ -388,7 +388,8 @@ module.exports = {
   getIsGlobalScope(ancestors) {
     for (let parent of ancestors) {
       if (parent.type == "FunctionExpression" ||
-          parent.type == "FunctionDeclaration") {
+          parent.type == "FunctionDeclaration" ||
+          parent.type == "ArrowFunctionExpression") {
         return false;
       }
     }