Notify VRDeviceProviders when there are pages listening for vrdisplayactivate

third_party/WebKit/Source/modules/vr/NavigatorVR.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NavigatorVR_h
 #define NavigatorVR_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "core/frame/DOMWindowProperty.h"
+#include "core/frame/LocalDOMWindow.h"
 #include "modules/ModulesExport.h"
 #include "modules/vr/VRDisplay.h"
 #include "modules/vr/VRDisplayEvent.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/WebVector.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
 class Document;
 class Navigator;
 class VRController;
 
 class MODULES_EXPORT NavigatorVR final
     : public GarbageCollectedFinalized<NavigatorVR>,
       public Supplement<Navigator>,
-      public DOMWindowProperty {
+      public DOMWindowProperty,
+      public LocalDOMWindow::EventListenerObserver {
   USING_GARBAGE_COLLECTED_MIXIN(NavigatorVR);
   WTF_MAKE_NONCOPYABLE(NavigatorVR);
 
  public:
   static NavigatorVR* from(Document&);
   static NavigatorVR& from(Navigator&);
   virtual ~NavigatorVR();
 
   static ScriptPromise getVRDisplays(ScriptState*, Navigator&);
   ScriptPromise getVRDisplays(ScriptState*);
 
   VRController* controller();
   Document* document();
 
   // Queues up event to be fired soon.
   void enqueueVREvent(VRDisplayEvent*);
 
   // Dispatches a user gesture event immediately.
   void dispatchVRGestureEvent(VRDisplayEvent*);
 
+  // Inherited from LocalDOMWindow::EventListenerObserver.
+  void didAddEventListener(LocalDOMWindow*, const AtomicString&) override;
+  void didRemoveEventListener(LocalDOMWindow*, const AtomicString&) override;
+  void didRemoveAllEventListeners(LocalDOMWindow*) override;
+
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class VRDisplay;
   friend class VRGetDevicesCallback;
 
   explicit NavigatorVR(LocalFrame*);
 
   static const char* supplementName();
 
   void fireVRDisplayPresentChange(VRDisplay*);
 
   Member<VRController> m_controller;
 };
 
 }  // namespace blink
 
 #endif  // NavigatorVR_h