diff -r 000000000000 -r 6474c204b198 dom/events/DragEvent.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/events/DragEvent.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,148 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/DragEvent.h"
+#include "mozilla/MouseEvents.h"
+#include "nsContentUtils.h"
+#include "prtime.h"
+
+namespace mozilla {
+namespace dom {
+
+DragEvent::DragEvent(EventTarget* aOwner,
+                     nsPresContext* aPresContext,
+                     WidgetDragEvent* aEvent)
+  : MouseEvent(aOwner, aPresContext,
+               aEvent ? aEvent : new WidgetDragEvent(false, 0, nullptr))
+{
+  if (aEvent) {
+    mEventIsInternal = false;
+  }
+  else {
+    mEventIsInternal = true;
+    mEvent->time = PR_Now();
+    mEvent->refPoint.x = mEvent->refPoint.y = 0;
+    mEvent->AsMouseEvent()->inputSource = nsIDOMMouseEvent::MOZ_SOURCE_UNKNOWN;
+  }
+}
+
+NS_IMPL_ADDREF_INHERITED(DragEvent, MouseEvent)
+NS_IMPL_RELEASE_INHERITED(DragEvent, MouseEvent)
+
+NS_INTERFACE_MAP_BEGIN(DragEvent)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMDragEvent)
+NS_INTERFACE_MAP_END_INHERITING(MouseEvent)
+
+void
+DragEvent::InitDragEvent(const nsAString& aType,
+                         bool aCanBubble,
+                         bool aCancelable,
+                         nsIDOMWindow* aView,
+                         int32_t aDetail,
+                         int32_t aScreenX,
+                         int32_t aScreenY,
+                         int32_t aClientX,
+                         int32_t aClientY,
+                         bool aCtrlKey,
+                         bool aAltKey,
+                         bool aShiftKey,
+                         bool aMetaKey,
+                         uint16_t aButton,
+                         EventTarget* aRelatedTarget,
+                         DataTransfer* aDataTransfer,
+                         ErrorResult& aError)
+{
+  aError =
+    MouseEvent::InitMouseEvent(aType, aCanBubble, aCancelable,
+                               aView, aDetail, aScreenX, aScreenY,
+                               aClientX, aClientY, aCtrlKey, aAltKey,
+                               aShiftKey, aMetaKey, aButton, aRelatedTarget);
+  if (aError.Failed()) {
+    return;
+  }
+
+  if (mEventIsInternal && mEvent) {
+    mEvent->AsDragEvent()->dataTransfer = aDataTransfer;
+  }
+}
+
+NS_IMETHODIMP
+DragEvent::InitDragEvent(const nsAString& aType,
+                         bool aCanBubble,
+                         bool aCancelable,
+                         nsIDOMWindow* aView,
+                         int32_t aDetail,
+                         int32_t aScreenX,
+                         int32_t aScreenY,
+                         int32_t aClientX,
+                         int32_t aClientY,
+                         bool aCtrlKey,
+                         bool aAltKey,
+                         bool aShiftKey,
+                         bool aMetaKey,
+                         uint16_t aButton,
+                         nsIDOMEventTarget* aRelatedTarget,
+                         nsIDOMDataTransfer* aDataTransfer)
+{
+  nsCOMPtr<DataTransfer> dataTransfer = do_QueryInterface(aDataTransfer);
+
+  nsresult rv =
+    MouseEvent::InitMouseEvent(aType, aCanBubble, aCancelable, aView, aDetail,
+                               aScreenX, aScreenY, aClientX, aClientY,
+                               aCtrlKey, aAltKey, aShiftKey, aMetaKey, aButton,
+                               aRelatedTarget);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (mEventIsInternal && mEvent) {
+    mEvent->AsDragEvent()->dataTransfer = dataTransfer;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DragEvent::GetDataTransfer(nsIDOMDataTransfer** aDataTransfer)
+{
+  NS_IF_ADDREF(*aDataTransfer = GetDataTransfer());
+  return NS_OK;
+}
+
+DataTransfer*
+DragEvent::GetDataTransfer()
+{
+  // the dataTransfer field of the event caches the DataTransfer associated
+  // with the drag. It is initialized when an attempt is made to retrieve it
+  // rather that when the event is created to avoid duplicating the data when
+  // no listener ever uses it.
+  if (!mEvent || mEvent->eventStructType != NS_DRAG_EVENT) {
+    NS_WARNING("Tried to get dataTransfer from non-drag event!");
+    return nullptr;
+  }
+
+  WidgetDragEvent* dragEvent = mEvent->AsDragEvent();
+  // for synthetic events, just use the supplied data transfer object even if null
+  if (!mEventIsInternal) {
+    nsresult rv = nsContentUtils::SetDataTransferInEvent(dragEvent);
+    NS_ENSURE_SUCCESS(rv, nullptr);
+  }
+
+  return dragEvent->dataTransfer;
+}
+
+} // namespace dom
+} // namespace mozilla
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+nsresult
+NS_NewDOMDragEvent(nsIDOMEvent** aInstancePtrResult,
+                   EventTarget* aOwner,
+                   nsPresContext* aPresContext,
+                   WidgetDragEvent* aEvent) 
+{
+  DragEvent* event = new DragEvent(aOwner, aPresContext, aEvent);
+  return CallQueryInterface(event, aInstancePtrResult);
+}