Steps to reproduce:

1. Using a Nightly build go to about:config and set the following prefs:
   browser.newtabpage.activity-stream.asrouter.devtoolsEnabled = true
   browser.newtabpage.activity-stream.asrouter.providers.onboarding set to:
   {"id":"onboarding","type":"local","localProvider":"OnboardingMessageProvider","enabled":true,"exclude":[]}
2. Go to about:newtab#asrouter, Targeting tab and scroll to the bottom of the page
3. Select Force Attribution and open a new tab with about:welcome url

Expected:
Upon going to about:welcome, the first page of return to amo page should be shown (+ Add the Extension)

Actual:
Restart is required each time we change the attribution, there is a high chance that this issue will not manifest in prod because only one extension will be attributed, thus the low priority.

This is used for testing purposes only so assigning lower priority.

I don't see any benefits from fixing this bug, the purpose of the router devtools is to get the message to show in order to test that it matches the design spec. Other functionality should be tested by simulating the real user action.