Disable Perf Insights subpanel, collapse sidebar by default

Author: huntie

front_end/panels/timeline/TimelinePanel.ts

@@ -772,7 +772,7 @@ export class TimelinePanel extends UI.Panel.Panel implements Client, TimelineMod
   #setActiveInsight(insight: TimelineComponents.Sidebar.ActiveInsight|null): void {
     // When an insight is selected, ensure that the 3P checkbox is disabled
     // to avoid dimming interference.
-    if (insight) {
+    if (insight && !Root.Runtime.experiments.isEnabled(Root.Runtime.ExperimentName.REACT_NATIVE_SPECIFIC_UI)) {
       this.#splitWidget.showBoth();
     }
     this.#sideBar.setActiveInsight(insight);
@@ -2185,6 +2185,10 @@ export class TimelinePanel extends UI.Panel.Panel implements Client, TimelineMod
       // Used in interaction tests & screenshot tests.
       return;
     }
+    // [RN] Keep sidebar collapsed by default
+    if (Root.Runtime.experiments.isEnabled(Root.Runtime.ExperimentName.REACT_NATIVE_SPECIFIC_UI)) {
+      return;
+    }
     const needToRestore = this.#restoreSidebarVisibilityOnTraceLoad;
     const userHasSeenSidebar = this.#sideBar.userHasOpenedSidebarOnce();