VR: Add stub WebVR warnings.

chrome/browser/android/vr_shell/ui_scene_manager.h

Index: chrome/browser/android/vr_shell/ui_scene_manager.h
diff --git a/chrome/browser/android/vr_shell/ui_scene_manager.h b/chrome/browser/android/vr_shell/ui_scene_manager.h
index b066bd28330ad9e234e52f7392f4bc40c557f163..df979c4fb3c7c2e79585dbf5f8a7ab3fd08e9cd8 100644
--- a/chrome/browser/android/vr_shell/ui_scene_manager.h
+++ b/chrome/browser/android/vr_shell/ui_scene_manager.h
@@ -7,10 +7,12 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/timer/timer.h"
 #include "base/values.h"
 
 namespace vr_shell {
 
+struct UiElement;
 class UiScene;
 
 class UiSceneManager {
@@ -26,11 +28,20 @@ class UiSceneManager {
   void SetWebVRMode(bool web_vr);
 
  private:
+  void ConfigureSecurityWarnings();
+  void OnSecurityWarningTimer();
+
   UiScene* scene_;
 
+  // UI elemenet pointers (not owned by the scene manager).
+  UiElement* permanent_security_warning_ = nullptr;
+  UiElement* transient_security_warning_ = nullptr;
+
   bool web_vr_mode_ = false;
   bool secure_origin_ = false;
 
+  base::OneShotTimer security_warning_timer_;
+
   base::WeakPtrFactory<UiSceneManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UiSceneManager);