chromium/ui/webui/resources/js/browser_command/README

This directory contains the Mojo definitions for the NTP promo browser commands,
i.e, the set of browser commands sent by the NTP promos and understood by the
browser. These commands may trigger side-effect-free actions in the browser such
as navigating to a chrome:// URL or initiating a helpful flow.

These mojo definitions are accessible to Desktop and Android. The implementer of
the handler interface in browser_command.mojom chooses which commands to
handle and which ones to ignore depending on the platform or the milestone.

The Desktop implementations for these commands are located at:
//chrome/browser/ui/webui/new_tab_page/promo_browser_command/