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);
@@ skipping 11 matching lines @@
 void VRServiceImpl::OnVRDisplayInfoCreated(
     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.

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

Would be nice to call out (until we fix it) the reason that we can get null
display info (because libraries don't exist etc).

[tiborg, 2017/03/27 14:53:25]

Added a comment to clarify.

+    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