Step 1.75: Include the PhantomJS Mink driver

That was not so simple with the new merge plugin for composer.

Steps to do this:

1. Apply patch to core/lib/Drupal/Core/Composer/Composer.php
2. Do composer require --dev jcalderonzumba/gastonjs in Drupal root
3. Move package from composer.json to core/composer.json
4. Do composer update nothing to fix hashes

We're adding this library for testing purposes so I think this is rc eligible.

Looks like this has sign-off from a framework manager (obviously :P). It is in core for the purpose of making testing better. From the sound of it on the ground here at the BADCamp authoring experience summit, the more tools we have available for this kind of stuff in core, the better off contrib is going to be, so works from a "contrib project (soft) blocker" POV as well.

Committed and pushed to 8.0.x. Thanks!

WOOOOT! Front-end testing getting closer than ever!