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

chrome/browser/android/vr_shell/vr_shell.cc

Index: chrome/browser/android/vr_shell/vr_shell.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell.cc b/chrome/browser/android/vr_shell/vr_shell.cc
index ab3b67ac4529a57e6708f2c6ea1ef9543128f90a..dc0d2af29fc21b24a2c92aa27be319558321f95c 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -366,6 +366,13 @@ void VrShell::RestoreContentSurface(JNIEnv* env,
       base::Bind(&VrShellGl::CreateContentSurface, gl_thread_->GetVrShellGl()));
 }
 
+void VrShell::SetHistoryButtonsEnabled(JNIEnv* env,
+                                       const JavaParamRef<jobject>& obj,
+                                       jboolean can_go_back,
+                                       jboolean can_go_forward) {
+  html_interface_->SetHistoryButtonsEnabled(can_go_back, can_go_forward);
+}
+
 void VrShell::UiSurfaceChanged(jobject surface) {
   ui_compositor_->SurfaceChanged(surface);
 }