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

device/vr/vr_display_impl.cc

 // 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.
 
 #include <utility>
 
 #include "base/bind.h"
 #include "device/vr/vr_device.h"
 #include "device/vr/vr_device_manager.h"
 #include "device/vr/vr_service_impl.h"
@@ skipping 27 matching lines @@
 }
 
 void VRDisplayImpl::OnBlur() {
   client_->OnBlur();
 }
 
 void VRDisplayImpl::OnFocus() {
   client_->OnFocus();
 }
 
-void VRDisplayImpl::OnActivate(mojom::VRDisplayEventReason reason) {
+void VRDisplayImpl::OnActivate(mojom::VRDisplayEventReason reason,
+                               const base::Callback<void(bool)>& on_handled) {
   VRDeviceManager* manager = VRDeviceManager::GetInstance();
   if (!manager->IsMostRecentlyListeningForActivate(service_))
     return;
-  client_->OnActivate(reason);
+  client_->OnActivate(reason, on_handled);
 }
 
 void VRDisplayImpl::OnDeactivate(mojom::VRDisplayEventReason reason) {
   client_->OnDeactivate(reason);
 }
 
 void VRDisplayImpl::RequestPresent(bool secure_origin,
                                    mojom::VRSubmitFrameClientPtr submit_client,
                                    const RequestPresentCallback& callback) {
   // TODO(mthiesse): Re-enable insecure origin support once webVR content
@@ skipping 44 matching lines @@
                              source_height);
 }
 
 void VRDisplayImpl::GetVRVSyncProvider(mojom::VRVSyncProviderRequest request) {
   if (!device_->IsAccessAllowed(this)) {
     return;
   }
   device_->GetVRVSyncProvider(std::move(request));
 }
 }