Disable back button when stack is empty

chrome/browser/android/vr_shell/ui_elements/url_bar.cc

Index: chrome/browser/android/vr_shell/ui_elements/url_bar.cc
diff --git a/chrome/browser/android/vr_shell/ui_elements/url_bar.cc b/chrome/browser/android/vr_shell/ui_elements/url_bar.cc
index 1cd156a010994ad421f95fa6d457634254f80b22..72dcf1c081b9628a2aace64da7ef94d1d12c7797 100644
--- a/chrome/browser/android/vr_shell/ui_elements/url_bar.cc
+++ b/chrome/browser/android/vr_shell/ui_elements/url_bar.cc
@@ -83,6 +83,10 @@ void UrlBar::SetURL(const GURL& gurl) {
   texture_->SetURL(gurl);
 }
 
+void UrlBar::SetHistoryButtonsEnabled(bool can_go_back) {
+  texture_->SetHistoryButtonsEnabled(can_go_back);
+}
+
 void UrlBar::SetSecurityLevel(security_state::SecurityLevel level) {
   texture_->SetSecurityLevel(level);
 }