Bug 1597791: Introduce autoFillAdaptiveHistory nimbus variable. r=adw

Differential Revision: https://phabricator.services.mozilla.com/D145704

browser/components/urlbar/UrlbarPrefs.jsm

@@ -46,7 +46,8 @@ const PREF_URLBAR_DEFAULTS = new Map([
   // textbox.  If false, autofill will be disabled.
   ["autoFill", true],
 
-  // Whether enabling adaptive history autofill.
+  // Whether enabling adaptive history autofill. This pref is a fallback for the
+  // Nimbus variable `autoFillAdaptiveHistoryEnabled`.
   ["autoFill.adaptiveHistory.enabled", false],
 
   // Threshold for use count of input history that we handle as adaptive history

browser/components/urlbar/UrlbarProviderAutofill.jsm

@@ -752,7 +752,7 @@ class ProviderAutofill extends UrlbarProvider {
     }
 
     // We try to autofill with adaptive history first.
-    if (UrlbarPrefs.get("autoFill.adaptiveHistory.enabled")) {
+    if (UrlbarPrefs.get("autoFillAdaptiveHistoryEnabled")) {
       const [query, params] = this._getAdaptiveHistoryQuery(queryContext);
       if (query) {
         const resultSet = await conn.executeCached(query, params);

toolkit/components/nimbus/FeatureManifest.yaml

@@ -34,6 +34,10 @@ urlbar:
     the event is recorded once per app session when the user first encounters
     the UI of the experiment in which they're enrolled.
   variables:
+    autoFillAdaptiveHistoryEnabled:
+      type: boolean
+      fallbackPref: browser.urlbar.autoFill.adaptiveHistory.enabled
+      description: Whether enabling adaptive history autofill.
     bestMatchBlockingEnabled:
       type: boolean
       fallbackPref: browser.urlbar.bestMatch.blockingEnabled