Conflict with Tracer module due to compiler pass

Problem/Motivation

If both the CAS module and the Tracer module v 1.1.0 and up (dependency of the Webprofiler module) are installed, you cannot clear cache as the when the service container is compiled, a ServiceNotFoundException is thrown in the CAS module's DeprecatedEventConstants.php class when it tries to load the `event_dispatcher` service:

Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "event_dispatcher". in Symfony\Component\DependencyInjection\ContainerBuilder->getDefinition() (line 1042 of /vendor/symfony/dependency-injection/ContainerBuilder.php).

I guess this is because the Tracer module also has a compiler pass that decorates the event dispatcher which executes before CAS' compiler pass. I don't know why decorating a service prevents the service from being loaded in this compiler pass though?

Steps to reproduce

Install both CAS 3.0.0-beta4 and Tracer 1.2.1. Clear cache. Observe ServiceNotFoundException.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes