Control visibility of 2D VR menu buttons using native state.

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 e024aab4dc8ab5b8ebf32e1dfde3d5f858db1463..d4e5cf2979ce60cb9f8dd5a9767d9ea2c4fe6b1f 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -762,8 +762,10 @@ void VrShell::SetWebVrMode(JNIEnv* env,
     int64_t now = gvr::GvrApi::GetTimePointNow().monotonic_system_time_nanos;
     constexpr int64_t seconds_to_nanos = 1000 * 1000 * 1000;
     webvr_warning_end_nanos_ = now + kWebVrWarningSeconds * seconds_to_nanos;
+    html_interface_->SetMode(UiInterface::Mode::WEB_VR);
   } else {
     webvr_warning_end_nanos_ = 0;
+    html_interface_->SetMode(UiInterface::Mode::STANDARD);
   }
 }