Implement a means of letting native VR Shell control the HTML UI.

chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h

Index: chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h
diff --git a/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h b/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h
index 36d081170f7dab8bd9bb48ac46da312feb1f0cce..fb32a64cc16a7d827153a6067c08430aa3e59578 100644
--- a/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h
+++ b/chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h
@@ -22,6 +22,8 @@ class VrShellUIMessageHandler : public content::WebUIMessageHandler {
   VrShellUIMessageHandler();
   ~VrShellUIMessageHandler() override;
 
+  content::WebUI* GetWebUi() { return web_ui(); }
+
  private:
   // content::WebUIMessageHandler:
   void RegisterMessages() override;
@@ -32,6 +34,8 @@ class VrShellUIMessageHandler : public content::WebUIMessageHandler {
 
   base::WeakPtr<vr_shell::VrShell> vr_shell_;
 
+  base::WeakPtrFactory<VrShellUIMessageHandler> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(VrShellUIMessageHandler);
 };