Let HTML UI manage menu mode.

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 62d5605562671f16ee5947c96d325030b564c4ba..2ba662615a50254a339c4ae690b5c8f20f23b947 100644
--- a/chrome/browser/android/vr_shell/ui_interface.cc
+++ b/chrome/browser/android/vr_shell/ui_interface.cc
@@ -27,11 +27,6 @@ void UiInterface::SetMode(Mode mode) {
   FlushModeState();
 }
 
-void UiInterface::SetMenuMode(bool enabled) {
-  menu_mode_ = enabled;
-  FlushModeState();
-}
-
 void UiInterface::SetFullscreen(bool enabled) {
   fullscreen_ = enabled;
   FlushModeState();
@@ -49,7 +44,6 @@ void UiInterface::SetOmniboxSuggestions(
 
 void UiInterface::FlushModeState() {
   updates_.SetInteger("mode", static_cast<int>(mode_));
-  updates_.SetBoolean("menuMode", menu_mode_);
   updates_.SetBoolean("fullscreen", fullscreen_);
   FlushUpdates();
 }
@@ -117,6 +111,11 @@ void UiInterface::SetURL(const GURL& url) {
   FlushUpdates();
 }
 
+void UiInterface::HandleAppButtonClicked() {
+  updates_.SetBoolean("appButtonClicked", true);
+  FlushUpdates();
+}
+
 void UiInterface::OnDomContentsLoaded() {
   loaded_ = true;
 #if defined(ENABLE_VR_SHELL_UI_DEV)