Bug 1945927 - Ensure that resize observer is restored when reinitializing revamped sidebar. r=sidebar-reviewers,kcochrane

Differential Revision: https://phabricator.services.mozilla.com/D236933

browser/components/sidebar/SidebarState.sys.mjs

@@ -286,9 +286,10 @@ export class SidebarState {
       this.#props.launcherExpanded = false;
       return;
     }
+    const previousExpanded = this.#props.launcherExpanded;
     this.#props.launcherExpanded = expanded;
     this.#launcherEl.expanded = expanded;
-    if (expanded) {
+    if (expanded && !previousExpanded) {
       Glean.sidebar.expand.record();
     }
     // Marking the tab container element as expanded or not simplifies the CSS logic

browser/components/sidebar/browser-sidebar.js

@@ -364,6 +364,7 @@ var SidebarController = {
     }
     if (this._mainResizeObserver) {
       this._mainResizeObserver.disconnect();
+      this._mainResizeObserverAdded = false;
     }
     this._mainResizeObserver = new ResizeObserver(([entry]) =>
       this._handleLauncherResize(entry)