Use the Mojo StubBindings interface correctly in WebUSB LayoutTests.

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

Index: third_party/WebKit/Source/modules/webusb/USB.cpp
diff --git a/third_party/WebKit/Source/modules/webusb/USB.cpp b/third_party/WebKit/Source/modules/webusb/USB.cpp
index 8f4ec193593544030640364e46fbfb2017f3423b..72ea07bb53310bf73148e23a294b7a9a22449904 100644
--- a/third_party/WebKit/Source/modules/webusb/USB.cpp
+++ b/third_party/WebKit/Source/modules/webusb/USB.cpp
@@ -164,6 +164,11 @@ void USB::onGetPermission(ScriptPromiseResolver* resolver, usb::DeviceInfoPtr de
     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));