Fixes crash where the browser crashed when visiting WebVR pages without VR Services installed.

device/vr/vr_service_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 "device/vr/vr_service_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
@@ skipping 18 matching lines @@
   mojo::MakeStrongBinding(base::MakeUnique<VRServiceImpl>(),
                           std::move(request));
 }
 
 void VRServiceImpl::SetClient(mojom::VRServiceClientPtr service_client,
                               const SetClientCallback& callback) {
   DCHECK(!client_.get());
   client_ = std::move(service_client);
   VRDeviceManager* device_manager = VRDeviceManager::GetInstance();
   // Once a client has been connected AddService will force any VRDisplays to
-  // send OnConnected to it so that it's populated with the currently active
-  // displays. Thereafer it will stay up to date by virtue of listening for new
+  // send ConnectDevice to it so that it's populated with the currently active
+  // displays. Thereafter it will stay up to date by virtue of listening for new
   // connected events.
   device_manager->AddService(this);
   callback.Run(device_manager->GetNumberOfConnectedDevices());
 }
 
 void VRServiceImpl::ConnectDevice(VRDevice* device) {
   DCHECK(displays_.count(device) == 0);
   base::Callback<void(mojom::VRDisplayInfoPtr)> on_created =
       base::Bind(&VRServiceImpl::OnVRDisplayInfoCreated,
                  weak_ptr_factory_.GetWeakPtr(), device);
   device->CreateVRDisplayInfo(on_created);
 }
 
 void VRServiceImpl::SetListeningForActivate(bool listening) {
   listening_for_activate_ = listening;
   VRDeviceManager* device_manager = VRDeviceManager::GetInstance();
   device_manager->ListeningForActivateChanged(listening);
 }
 
 // Creates a VRDisplayPtr unique to this service so that the associated page can
 // communicate with the VRDevice.
 void VRServiceImpl::OnVRDisplayInfoCreated(

[amp, 2017/03/24 21:51:09]

This might have been something from the previous change, but why is
onVRDisplayInfoCreated getting called at all if we don't have any VR libraries
(and shouldn't have any available VR Devices)?

I'm confused.

Should we be changing that flow instead of adjusting the code here?

[billorr, 2017/03/24 22:06:54]

Long term (post Windows refactor) the device shouldn't be created if we don't
have a delegate.

[tiborg, 2017/03/24 22:16:36]

Yep, currently this is the workaround to say that the device does not exist. I
agree, it would be better if we don't create this device in the first place.

[amp, 2017/03/24 22:33:31]

Ok, I'm fine with addressing this in a future refactor.

     VRDevice* device,
     mojom::VRDisplayInfoPtr display_info) {
   // TODO(crbug/701027): make sure that client_ is never null by initializing it
   // in the constructor.
   if (!client_) {
     DLOG(ERROR) << "Cannot create VR display because connection to render "
                    "process is not established";
     return;
   }
+  if (!display_info) {
+    // We cannot instantiate a display with a null display info.
+    DLOG(WARNING)

[billorr, 2017/03/24 21:46:55]

NIT: Warning sounds like this is an invalid state, but this can happen for
legitimate reasons.

[tiborg, 2017/03/24 22:16:36]

Removed the warning.

+        << "Received null display info. Will not instantiate VRDisplayImpl.";
+    return;
+  }
   displays_[device] = base::MakeUnique<VRDisplayImpl>(
       device, this, client_.get(), std::move(display_info));
 }
 
 VRDisplayImpl* VRServiceImpl::GetVRDisplayImplForTesting(VRDevice* device) {
   auto it = displays_.find(device);
   return (it == displays_.end()) ? nullptr : it->second.get();
 }
 
 }  // namespace device