Tentatively goes into WebVR presentation mode if page listens to vrdisplayactivate.

device/vr/vr_display_impl.h

 // Copyright 2016 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 DEVICE_VR_VR_DISPLAY_IMPL_H
 #define DEVICE_VR_VR_DISPLAY_IMPL_H
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 17 matching lines @@
   VRDisplayImpl(device::VRDevice* device,
                 VRServiceImpl* service,
                 mojom::VRServiceClient* service_client,
                 mojom::VRDisplayInfoPtr display_info);
   ~VRDisplayImpl() override;
 
   virtual void OnChanged(mojom::VRDisplayInfoPtr vr_device_info);
   virtual void OnExitPresent();
   virtual void OnBlur();
   virtual void OnFocus();
-  virtual void OnActivate(mojom::VRDisplayEventReason reason);
+  virtual void OnActivate(mojom::VRDisplayEventReason reason,
+                          const base::Callback<void(bool)>& on_handled);
   virtual void OnDeactivate(mojom::VRDisplayEventReason reason);
 
  private:
   friend class VRDisplayImplTest;
   friend class VRServiceImpl;
 
   void RequestPresent(bool secure_origin,
                       mojom::VRSubmitFrameClientPtr submit_client,
                       const RequestPresentCallback& callback) override;
   void ExitPresent() override;
@@ skipping 15 matching lines @@
   mojom::VRDisplayClientPtr client_;
   device::VRDevice* device_;
   VRServiceImpl* service_;
 
   base::WeakPtrFactory<VRDisplayImpl> weak_ptr_factory_;
 };
 
 }  // namespace device
 
 #endif  //  DEVICE_VR_VR_DISPLAY_IMPL_H