Bug 1403961, part 2 - Fix and enable eslint for ipc/. r=billm

After the previous patch, all that is needed to pass eslint is some
whitespace fixes I generated using:
  ./mach eslint --fix ipc

The .eslintrc.js file makes eslint expect XPCShell global variables.

With those two changes, eslint can be enabled for the ipc/ directory.

MozReview-Commit-ID: BqSICp2iV6O

--HG--
extra : rebase_source : ccab8be9fc1ae1116ae55631d3978c39d35cad05

.eslintignore

@@ -18,7 +18,6 @@ extensions/universalchardet/**
 gfx/**
 image/**
 intl/**
-ipc/**
 layout/**
 media/**
 memory/**

ipc/testshell/tests/.eslintrc.js

@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "plugin:mozilla/xpcshell-test"
+  ]
+};