ASRouter listens to enrollment changes

foo.patch

--- a/browser/components/newtab/lib/ASRouter.jsm
+++ b/browser/components/newtab/lib/ASRouter.jsm
@@ -98,7 +98,7 @@ const JEXL_PROVIDER_CACHE = new Set(["snippets"]);

 // To observe the app locale change notification.
 const TOPIC_INTL_LOCALE_CHANGED = "intl:app-locales-changed";
-const TOPIC_EXPERIMENT_FORCE_ENROLLED = "nimbus:force-enroll";
+const NIMBUS_TOPICS = ["nimbus:enroll", "nimbus:unenroll"];
 // To observe the pref that controls if ASRouter should use the remote Fluent files for l10n.
 const USE_REMOTE_L10N_PREF =
   "browser.newtabpage.activity-stream.asrouter.useRemoteL10n";
@@ -627,7 +627,7 @@ class _ASRouter {
     this.isUnblockedMessage = this.isUnblockedMessage.bind(this);
     this.unblockAll = this.unblockAll.bind(this);
     this.forceWNPanel = this.forceWNPanel.bind(this);
-    this._onExperimentForceEnrolled = this._onExperimentForceEnrolled.bind(
+    this._onExperimentEnrollmentChanged = this._onExperimentEnrollmentChanged.bind(
       this
     );
     this.forcePBWindow = this.forcePBWindow.bind(this);
@@ -1041,10 +1041,9 @@ class _ASRouter {

     lazy.SpecialMessageActions.blockMessageById = this.blockMessageById;
     Services.obs.addObserver(this._onLocaleChanged, TOPIC_INTL_LOCALE_CHANGED);
-    Services.obs.addObserver(
-      this._onExperimentForceEnrolled,
-      TOPIC_EXPERIMENT_FORCE_ENROLLED
-    );
+    for (const topic of NIMBUS_TOPICS) {
+      Services.obs.addObserver(this._onExperimentEnrollmentChanged, topic);
+    }
     Services.prefs.addObserver(USE_REMOTE_L10N_PREF, this);
     // sets .initialized to true and resolves .waitForInitialized promise
     this._finishInitializing();
@@ -1074,10 +1073,9 @@ class _ASRouter {
       this._onLocaleChanged,
       TOPIC_INTL_LOCALE_CHANGED
     );
-    Services.obs.removeObserver(
-      this._onExperimentForceEnrolled,
-      TOPIC_EXPERIMENT_FORCE_ENROLLED
-    );
+    for (const topic of NIMBUS_TOPICS) {
+      Services.obs.removeObserver(this._onExperimentEnrollmentChanged, topic);
+    }
     Services.prefs.removeObserver(USE_REMOTE_L10N_PREF, this);
     // If we added any CFR recommendations, they need to be removed
     CFRPageActions.clearRecommendations();
@@ -1987,7 +1985,7 @@ class _ASRouter {
     await lazy.ToolbarPanelHub._hideToolbarButton(win);
   }

-  async _onExperimentForceEnrolled(subject, topic, slug) {
+  async _onExperimentEnrollmentChanged(subject, topic, slug) {
     const experimentProvider = this.state.providers.find(
       p => p.id === "messaging-experiments"
     );

--- a/toolkit/components/nimbus/lib/ExperimentManager.jsm
+++ b/toolkit/components/nimbus/lib/ExperimentManager.jsm
@@ -402,6 +402,7 @@ class _ExperimentManager {
       this.setExperimentActive(experiment);
     }
     this.sendEnrollmentTelemetry(experiment);
+    Services.obs.notifyObservers(null, "nimbus:enroll", slug);

     this._setEnrollmentPrefs(prefsToSet);
     this._updatePrefObservers(experiment);
@@ -452,8 +453,6 @@ class _ExperimentManager {
       { force: true }
     );

-    Services.obs.notifyObservers(null, "nimbus:force-enroll", slug);
-
     return enrollment;
   }

@@ -480,6 +479,7 @@ class _ExperimentManager {
     if (!branch) {
       // Our branch has been removed. Unenroll.
       this.unenroll(recipe.slug, "branch-removed");
+      Services.obs.notifyObservers(null, "nimbus:unenroll", recipe.slug);
     }

     return true;