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 925995a81270be72fc69ce95f173cda5305ab38d..df63f3323e1172fb3d7a7ec4cafbc380a3f3261d 100644
--- a/chrome/browser/android/vr_shell/ui_scene_manager.cc
+++ b/chrome/browser/android/vr_shell/ui_scene_manager.cc
@@ -458,7 +458,9 @@ 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();