Bug 1453381 - Enable eslint for Marionette xpcshell tests. r=whimboo

There are currently two exceptions from the normal linting rules
that applies to Marionette xpcshell unit tests:

  - We use camel-casing for our test names.

  - We have many lines longer than 78 characters.

MozReview-Commit-ID: 4MykQujk9lR

--HG--
extra : rebase_source : f73e1a8d205eb34d1463f4805ba0fa806f150081

.eslintignore

@@ -343,7 +343,6 @@ services/sync/services-sync.js
 servo/**
 
 # Remote protocol exclusions
-testing/marionette/test_*.js
 testing/marionette/atom.js
 testing/marionette/legacyaction.js
 testing/marionette/client

testing/marionette/test/unit/.eslintrc.js

@@ -0,0 +1,13 @@
+"use strict";
+
+module.exports = {
+  "extends": ["plugin:mozilla/xpcshell-test"],
+  "rules": {
+    "camelcase": "off",
+    "max-len": ["error", 100, {
+      "ignoreStrings": true,
+      "ignoreTemplateLiterals": true,
+      "ignoreUrls": true,
+    }],
+  },
+};