Prevent new events from being sent to WebVR pages that are being closed.

device/vr/vr_device.cc

 // 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.
 
 #include "device/vr/vr_device.h"
 #include "device/vr/vr_device_provider.h"
 #include "device/vr/vr_service_impl.h"
 
 namespace device {
 
@@ skipping 13 matching lines @@
 
 void VRDevice::SetSecureOrigin(bool secure_origin) {}
 
 void VRDevice::AddService(VRServiceImpl* service) {
   // Create a VRDisplayImpl for this service/device pair
   VRDisplayImpl* display_impl = service->GetVRDisplayImpl(this);
   displays_.insert(std::make_pair(service, display_impl));
 }
 
 void VRDevice::RemoveService(VRServiceImpl* service) {
+  displays_.erase(service);
   if (IsPresentingService(service))
     ExitPresent();
-  displays_.erase(service);
 }
 
 bool VRDevice::IsAccessAllowed(VRServiceImpl* service) {
   return (!presenting_service_ || presenting_service_ == service);
 }
 
 bool VRDevice::IsPresentingService(VRServiceImpl* service) {
   return (presenting_service_ && presenting_service_ == service);
 }
 
@@ skipping 32 matching lines @@
 void VRDevice::OnDeactivate(mojom::VRDisplayEventReason reason) {
   for (const auto& display : displays_)
     display.second->client()->OnDeactivate(reason);
 }
 
 void VRDevice::SetPresentingService(VRServiceImpl* service) {
   presenting_service_ = service;
 }
 
 }  // namespace device