chromium/chrome/notification_helper/README.md

This directory contains the code for a COM server to handle native notification
activation. This code is compiled in an executable named notification_helper.exe.

This is a standalone executable. It launches Chrome using a certain command line.

This executable is designed to be launched by COM only. It is launched when a
toast is activated from the Windows Action Center. Once running, the process
registers the NotificationActivator class object to a COM module. This allows
COM to create the object and call its Activate() method to handle toast
activation when required. Once COM finishes the work, the NotificationActivator
class is unregistered from the module. The process then exits.

A NotificationActivator's CLSID depends on its Chrome channel, allowing
different NotificationActivators to be created per Chrome channel.