Add onconnect and ondisconnect events to navigator.usb.

Source/modules/webusb/USB.cpp

Index: Source/modules/webusb/USB.cpp
diff --git a/Source/modules/webusb/USB.cpp b/Source/modules/webusb/USB.cpp
index 5acd9acac742004e5bd733717f624432d60d89da..260993d483de01002f8bf87a4a47ca36cf47875d 100644
--- a/Source/modules/webusb/USB.cpp
+++ b/Source/modules/webusb/USB.cpp
@@ -11,6 +11,7 @@
 #include "core/dom/DOMException.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
+#include "modules/EventTargetModules.h"
 #include "modules/webusb/USBDevice.h"
 #include "modules/webusb/USBDeviceFilter.h"
 #include "modules/webusb/USBDeviceRequestOptions.h"
@@ -108,9 +109,20 @@ ScriptPromise USB::requestDevice(ScriptState* scriptState, const USBDeviceReques
     return promise;
 }
 
+ExecutionContext* USB::executionContext() const
+{
+    return m_controller->frame()->document();

[haraken, 2015/08/20 00:31:31]

m_controller->frame() can be null if the frame was detached.

  return m_controller->frame() ? m_controller->frame()->document() : nullptr;

+}
+
+const AtomicString& USB::interfaceName() const
+{
+    return EventTargetNames::USB;
+}
+
 DEFINE_TRACE(USB)
 {
     visitor->trace(m_controller);
+    RefCountedGarbageCollectedEventTargetWithInlineData<USB>::trace(visitor);
 }
 
 } // namespace blink