Use the Mojo StubBindings interface correctly in WebUSB LayoutTests.

third_party/WebKit/Source/modules/webusb/USB.cpp

 // 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 "modules/webusb/USB.h"
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/Document.h"
@@ skipping 146 matching lines @@
     }
     resolver->resolve(devices);
     m_deviceManagerRequests.remove(resolver);
 }
 
 void USB::onGetPermission(ScriptPromiseResolver* resolver, usb::DeviceInfoPtr deviceInfo)
 {
     if (!isActive(resolver))
         return;
 
+    if (!m_deviceManager) {

[haraken, 2016/05/04 03:26:15]

Does this mean that USB::onGetPermission can be called after the execution
context is destroyed?

[Reilly Grant (use Gerrit), 2016/05/04 18:20:41]

No, the issue is that m_deviceManager and m_chooserService are different pipes.
If one is closed by the browser process (for any reason, in this case it was a
bug in the test script) then a request may still complete on the other. This is
not likely to happen in production but is still worth guarding again.

+        resolver->reject(DOMException::create(NotFoundError, kNoServiceError));
+        return;
+    }
+
     if (deviceInfo) {
         usb::DevicePtr device;
         m_deviceManager->GetDevice(deviceInfo->guid, mojo::GetProxy(&device));
         resolver->resolve(USBDevice::create(std::move(deviceInfo), std::move(device), resolver->getExecutionContext()));
     } else {
         resolver->reject(DOMException::create(NotFoundError, "No device selected."));
     }
 }
 
 void USB::onDeviceChanges(usb::DeviceChangeNotificationPtr notification)
 {
     m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, WeakPersistentThisPointer<USB>(this))));

[haraken, 2016/05/04 03:26:15]

I'm wondering why you don't need the if(!m_deviceManager) check here.

[Reilly Grant (use Gerrit), 2016/05/04 18:22:32]

Since this method is called to handle a message arriving on the pipe held by
m_deviceManager it is guaranteed that m_deviceManager will not be null. Note
that in my next change this stops being the case and I have to add the check.

     for (auto& deviceInfo : notification->devices_added.PassStorage()) {
         usb::DevicePtr device;
         m_deviceManager->GetDevice(deviceInfo->guid, mojo::GetProxy(&device));
         dispatchEvent(USBConnectionEvent::create(EventTypeNames::connect, USBDevice::create(std::move(deviceInfo), std::move(device), getExecutionContext())));
     }
     for (auto& deviceInfo : notification->devices_removed.PassStorage())
         dispatchEvent(USBConnectionEvent::create(EventTypeNames::disconnect, USBDevice::create(std::move(deviceInfo), nullptr, getExecutionContext())));
 }
 
 void USB::onDeviceManagerConnectionError()
@@ skipping 18 matching lines @@
 
 DEFINE_TRACE(USB)
 {
     EventTargetWithInlineData::trace(visitor);
     ContextLifecycleObserver::trace(visitor);
     visitor->trace(m_deviceManagerRequests);
     visitor->trace(m_chooserServiceRequests);
 }
 
 } // namespace blink