Enable the object-shorthand ESLint rule

Please see http://eslint.org/docs/rules/object-shorthand.

Unfortunately, based on commit 9276d1dcd9, it seems that we still need to maintain compatibility with old Node.js versions, hence certain files/directories that are executed in Node.js are currently exempt from this rule.

Furthermore, since the files specific to the Chromium extension are not run through Babel, the `/extensions/chromium/` directory is also exempt from this rule.

test/unit/testreporter.js

@@ -24,13 +24,13 @@ var TestReporter = function(browser, appPath) {
   }
 
   function sendInfo(message) {
-    send('/info', {message: message});
+    send('/info', { message, });
   }
 
   function sendResult(status, description, error) {
     var message = {
-      status: status,
-      description: description
+      status,
+      description,
     };
     if (typeof error !== 'undefined') {
       message['error'] = error;