In bug 1868838, I missed a few modules:

• Spotlight: "resource://activity-stream/lib/Spotlight.jsm"
• ToastNotification: "resource://activity-stream/lib/ToastNotification.jsm"
• ToolbarBadgeHub: "resource://activity-stream/lib/ToolbarBadgeHub.jsm"
• ToolbarPanelHub: "resource://activity-stream/lib/ToolbarPanelHub.jsm"
• MomentsPageHub: "resource://activity-stream/lib/MomentsPageHub.jsm"
• InfoBar: "resource://activity-stream/lib/InfoBar.jsm"
• ActorConstants: "resource://activity-stream/common/ActorConstants.sys.mjs" (see this comment)
• InflightAssetsMessageProvider: "resource://testing-common/InflightAssetsMessageProvider.sys.mjs" (see this comment)

If I discover more, I'll update the above list.

All of the browser_asrouter tests under browser/components/newtab/test/browser also need to be moved.

We import the ActorConstants into the ASRouter unit-entry.js script because
ASRouterChild.sys.mjs loads ActorConstants.sys.mjs, and the ResourceUriPlugin
that does the rewriting for the Karma tests doesn't understand how to do
remapping outside of the newtab folder.

So instead of trying to hack that capability into ResourceUriPlugin, we
just import the ActorConstants into the Karma global scope.

I think the following modules in newtab/lib should be in the asrouter or aboutwelcome directory:

FeatureCalloutBroker.sys.mjs
FeatureCalloutMessages.sys.mjs
PageEventManager.sys.mjs

We can also move FeatureCallout.sys.mjs from browser/modules to asrouter now. The reason we put it there previously was because we didn't want to add more stuff to the newtab directory that had nothing to do with newtab. But now that we have our own directories, it makes sense to keep all the Feature Callout files together.

We can move styles from browser/components/newtab/content-src/styles to asrouter as well:

_feature-callout-theme.scss
_feature-callout.scss
_shopping.scss