Disable back button when stack is empty

chrome/browser/android/vr_shell/ui_scene_manager.cc

Index: chrome/browser/android/vr_shell/ui_scene_manager.cc
diff --git a/chrome/browser/android/vr_shell/ui_scene_manager.cc b/chrome/browser/android/vr_shell/ui_scene_manager.cc
index f7ccf44e4f39e77995020923ee066f1cefc82f1e..8fce01c4e8ba77db9f4b917b042ec0458be18b39 100644
--- a/chrome/browser/android/vr_shell/ui_scene_manager.cc
+++ b/chrome/browser/android/vr_shell/ui_scene_manager.cc
@@ -452,7 +452,9 @@ void UiSceneManager::SetIsExiting() {
 }
 
 void UiSceneManager::SetHistoryButtonsEnabled(bool can_go_back,
-                                              bool can_go_forward) {}
+                                              bool can_go_forward) {
+  url_bar_->SetHistoryButtonsEnabled(can_go_back);
+}
 
 void UiSceneManager::OnCloseButtonClicked() {
   browser_->ExitCct();