MB 419: Mullvad Browser migration procedures.

This commit implements the the Mullvad Browser's version of _migrateUI.

browser/components/BrowserGlue.sys.mjs

@@ -605,6 +605,9 @@ BrowserGlue.prototype = {
     // Base Browser-specific version of _migrateUI.
     this._migrateUIBB();
 
+    // Mullvad Browser-specific version of _migrateUI.
+    this._migrateUIMB();
+
     if (!Services.prefs.prefHasUserValue(PREF_PDFJS_ISDEFAULT_CACHE_STATE)) {
       lazy.PdfJs.checkIsDefault(this._isNewProfile);
     }
@@ -1877,6 +1880,37 @@ BrowserGlue.prototype = {
     Services.prefs.setIntPref(MIGRATION_PREF, MIGRATION_VERSION);
   },
 
+  // Use this method for any MB migration that can be run just before showing
+  // the UI.
+  // Anything that critically needs to be migrated earlier should not use this.
+  _migrateUIMB() {
+    // Version 1: Mullvad Browser 14.5a6: Clear home page update url preference
+    //            (mullvad-browser#411).
+    const MB_MIGRATION_VERSION = 1;
+    const MIGRATION_PREF = "mullvadbrowser.migration.version";
+
+    // If we decide to force updating users to pass through any version
+    // following 14.5, we can remove this check, and check only whether
+    // MIGRATION_PREF has a user value, like Mozilla does.
+    if (this._isNewProfile) {
+      // Do not migrate fresh profiles
+      Services.prefs.setIntPref(MIGRATION_PREF, MB_MIGRATION_VERSION);
+      return;
+    } else if (this._isNewProfile === undefined) {
+      // If this happens, check if upstream updated their function and do not
+      // set this member anymore!
+      console.error("_migrateUIMB: this._isNewProfile is undefined.");
+    }
+
+    const currentVersion = Services.prefs.getIntPref(MIGRATION_PREF, 0);
+
+    if (currentVersion < 1) {
+      Services.prefs.clearUserPref("mullvadbrowser.post_update.url");
+    }
+
+    Services.prefs.setIntPref(MIGRATION_PREF, MB_MIGRATION_VERSION);
+  },
+
   async _showUpgradeDialog() {
     const data = await lazy.OnboardingMessageProvider.getUpgradeMessage();
     const { gBrowser } = lazy.BrowserWindowTracker.getTopWindow();