File: vendor/symfony/symfony/src/Symfony/Bundle/FrameworkBundle/Resources/config/debug.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <parameters>
        <parameter key="debug.event_dispatcher.class">Symfony\Component\HttpKernel\Debug\TraceableEventDispatcher</parameter>
        <parameter key="debug.container.dump">%kernel.cache_dir%/%kernel.container_class%.xml</parameter>
        <parameter key="debug.controller_resolver.class">Symfony\Component\HttpKernel\Controller\TraceableControllerResolver</parameter>
        <parameter key="debug.error_handler.throw_at">-1</parameter>
    </parameters>

    <services>
        <service id="debug.event_dispatcher" class="%debug.event_dispatcher.class%">
            <tag name="monolog.logger" channel="event" />
            <argument type="service" id="debug.event_dispatcher.parent" />
            <argument type="service" id="debug.stopwatch" />
            <argument type="service" id="logger" on-invalid="null" />
        </service>

        <service id="debug.controller_resolver" class="%debug.controller_resolver.class%">
            <argument type="service" id="controller_resolver" />
            <argument type="service" id="debug.stopwatch" />
        </service>
    </services>
</container>