[IMP] web_tour: activate tour service for mobile

Before this commit, when you tried to run a tour by clicking on
"Start Tour" in the debug menu, nothing happened and a warning
message appeared in console:
"debug_manager.js:53 No handler for start_tour".
Now it will work on mobile too (debug mode only).

We had to do this to be able to run the main flow tour on mobile.

Note that another commit (in enterprise) will automatically consume
all tours to avoid to display it for demonstration purposes.

Task ID: 2149402