gh-13258: Implement new loading indicator (gh-13259)

src/zen/common/modules/ZenStartup.mjs

@@ -57,6 +57,7 @@ class ZenStartup {
       gZenWorkspaces.init();
       setTimeout(() => {
         gZenUIManager.init();
+        this.#initUIComponents();
         this.#checkForWelcomePage();
       }, 0);
     } catch (e) {
@@ -161,6 +162,16 @@ class ZenStartup {
     }
   }
 
+  #initUIComponents() {
+    const kUIComponents = ["ZenProgressBar"];
+    for (let component of kUIComponents) {
+      const module = ChromeUtils.importESModule(
+        "resource:///modules/zen/ui/" + component + ".sys.mjs"
+      );
+      new module[component](window);
+    }
+  }
+
   #checkForWelcomePage() {
     const kWelcomeScreenSeenPref = "zen.welcome-screen.seen";
     if (Services.env.get("MOZ_HEADLESS")) {