Visually disable VR Shell back/forward buttons when no history is available

chrome/browser/android/vr_shell/ui_interface.cc

Index: chrome/browser/android/vr_shell/ui_interface.cc
diff --git a/chrome/browser/android/vr_shell/ui_interface.cc b/chrome/browser/android/vr_shell/ui_interface.cc
index a61d448bd924f643a220d46bfe8fb52c40b79b72..6fdb6d9e51f1c50a11eb895502244df6279140f2 100644
--- a/chrome/browser/android/vr_shell/ui_interface.cc
+++ b/chrome/browser/android/vr_shell/ui_interface.cc
@@ -115,6 +115,13 @@ void UiInterface::HandleAppButtonClicked() {
   FlushUpdates();
 }
 
+void UiInterface::SetHistoryButtonsEnabled(bool can_go_back,
+                                           bool can_go_forward) {
+  updates_.SetBoolean("canGoBack", can_go_back);
+  updates_.SetBoolean("canGoForward", can_go_forward);
+  FlushUpdates();
+}
+
 void UiInterface::OnDomContentsLoaded() {
   loaded_ = true;
 #if defined(ENABLE_VR_SHELL_UI_DEV)