diff --git a/content/events/src/nsDOMDataTransfer.cpp b/content/events/src/nsDOMDataTransfer.cpp
index 36d9473d781..73f6ad0f4bc 100644
--- a/content/events/src/nsDOMDataTransfer.cpp
+++ b/content/events/src/nsDOMDataTransfer.cpp
@@ -74,6 +74,7 @@ nsDOMDataTransfer::nsDOMDataTransfer()
     mEffectAllowed(nsIDragService::DRAGDROP_ACTION_UNINITIALIZED),
     mReadOnly(PR_FALSE),
     mIsExternal(PR_FALSE),
+    mUserCancelled(PR_FALSE),
     mDragImageX(0),
     mDragImageY(0)
 {
@@ -84,6 +85,7 @@ nsDOMDataTransfer::nsDOMDataTransfer(PRUint32 aEventType, PRUint32 aAction)
     mDropEffect(nsIDragService::DRAGDROP_ACTION_NONE),
     mReadOnly(PR_TRUE),
     mIsExternal(PR_TRUE),
+    mUserCancelled(PR_FALSE),
     mDragImageX(0),
     mDragImageY(0)
 {
@@ -98,6 +100,7 @@ nsDOMDataTransfer::nsDOMDataTransfer(PRUint32 aEventType, PRUint32 aAction)
 nsDOMDataTransfer::nsDOMDataTransfer(PRUint32 aEventType,
                                      const PRUint32 aEffectAllowed,
                                      PRBool aIsExternal,
+                                     PRBool aUserCancelled,
                                      nsTArray<nsTArray<TransferItem> >& aItems,
                                      nsIDOMElement* aDragImage,
                                      PRUint32 aDragImageX,
@@ -107,6 +110,7 @@ nsDOMDataTransfer::nsDOMDataTransfer(PRUint32 aEventType,
     mEffectAllowed(aEffectAllowed),
     mReadOnly(PR_TRUE),
     mIsExternal(aIsExternal),
+    mUserCancelled(aUserCancelled),
     mItems(aItems),
     mDragImage(aDragImage),
     mDragImageX(aDragImageX),
@@ -207,6 +211,13 @@ nsDOMDataTransfer::SetEffectAllowedInt(PRUint32 aEffectAllowed)
   return  NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMDataTransfer::GetMozUserCancelled(PRBool* aUserCancelled)
+{
+  *aUserCancelled = mUserCancelled;
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMDataTransfer::GetTypes(nsIDOMDOMStringList** aTypes)
 {
@@ -453,11 +464,11 @@ nsDOMDataTransfer::AddElement(nsIDOMElement* aElement)
 }
 
 nsresult
-nsDOMDataTransfer::Clone(PRUint32 aEventType,
+nsDOMDataTransfer::Clone(PRUint32 aEventType, PRBool aUserCancelled,
                          nsIDOMDataTransfer** aNewDataTransfer)
 {
   nsDOMDataTransfer* newDataTransfer =
-    new nsDOMDataTransfer(aEventType, mEffectAllowed, mIsExternal,
+    new nsDOMDataTransfer(aEventType, mEffectAllowed, mIsExternal, aUserCancelled,
                           mItems, mDragImage, mDragImageX, mDragImageY);
   NS_ENSURE_TRUE(newDataTransfer, NS_ERROR_OUT_OF_MEMORY);
 
diff --git a/content/events/src/nsDOMDataTransfer.h b/content/events/src/nsDOMDataTransfer.h
index d09159f6684..669c264284d 100644
--- a/content/events/src/nsDOMDataTransfer.h
+++ b/content/events/src/nsDOMDataTransfer.h
@@ -94,6 +94,7 @@ protected:
   nsDOMDataTransfer(PRUint32 aEventType,
                     const PRUint32 aEffectAllowed,
                     PRBool aIsExternal,
+                    PRBool aUserCancelled,
                     nsTArray<nsTArray<TransferItem> >& aItems,
                     nsIDOMElement* aDragImage,
                     PRUint32 aDragImageX,
@@ -174,6 +175,9 @@ protected:
   // another application.
   PRPackedBool mIsExternal;
 
+  // true if the user cancelled the drag. Used only for the dragend event.
+  PRPackedBool mUserCancelled;
+
   // array of items, each containing an array of format->data pairs
   nsTArray<nsTArray<TransferItem> > mItems;
 
diff --git a/content/events/src/nsDOMDragEvent.cpp b/content/events/src/nsDOMDragEvent.cpp
index 292763eb87a..e159b913c3a 100644
--- a/content/events/src/nsDOMDragEvent.cpp
+++ b/content/events/src/nsDOMDragEvent.cpp
@@ -173,7 +173,7 @@ nsDOMDragEvent::GetDataTransfer(nsIDOMDataTransfer** aDataTransfer)
   nsCOMPtr<nsIDOMNSDataTransfer> initialDataTransferNS =
     do_QueryInterface(initialDataTransfer);
   NS_ENSURE_TRUE(initialDataTransferNS, NS_ERROR_FAILURE);
-  initialDataTransferNS->Clone(mEvent->message,
+  initialDataTransferNS->Clone(mEvent->message, dragEvent->userCancelled,
                                getter_AddRefs(dragEvent->dataTransfer));
   NS_ENSURE_TRUE(dragEvent->dataTransfer, NS_ERROR_OUT_OF_MEMORY);
 
diff --git a/content/events/test/test_dragstart.html b/content/events/test/test_dragstart.html
index 78ebdd8bf57..e6b5fb30197 100644
--- a/content/events/test/test_dragstart.html
+++ b/content/events/test/test_dragstart.html
@@ -155,6 +155,8 @@ function test_DataTransfer(dt)
   expectError(function() dt.mozSetDataAt("text/plain", "Some Text", 1),
               "NS_ERROR_DOM_INDEX_SIZE_ERR", "setDataAt index too high");
 
+  is(dt.mozUserCancelled, false, "userCancelled");
+
   // because an exception occured, the data should not have been added
   is(dt.mozItemCount, 0, "empty setDataAt index too high itemCount");
   dt.getData("text/plain", "", "empty setDataAt index too high getData");
diff --git a/dom/public/idl/events/nsIDOMDataTransfer.idl b/dom/public/idl/events/nsIDOMDataTransfer.idl
index c516f28e6a3..5505a7e9729 100644
--- a/dom/public/idl/events/nsIDOMDataTransfer.idl
+++ b/dom/public/idl/events/nsIDOMDataTransfer.idl
@@ -154,7 +154,7 @@ interface nsIDOMDataTransfer : nsISupports
   void addElement(in nsIDOMElement element);
 };
 
-[scriptable, uuid(A884E56C-1678-4978-AD20-142EE94108F5)]
+[scriptable, uuid(53C854FC-33F9-4647-B045-46D7AB06A6F1)]
 interface nsIDOMNSDataTransfer : nsISupports
 {
   /*
@@ -169,9 +169,11 @@ interface nsIDOMNSDataTransfer : nsISupports
   [noscript] attribute unsigned long effectAllowedInt;
 
   /**
-   * Creates a copy of the data transfer object
+   * Creates a copy of the data transfer object, for the given event type and
+   * user cancelled flag.
    */
-  [noscript] nsIDOMDataTransfer clone(in PRUint32 aEventType);
+  [noscript] nsIDOMDataTransfer clone(in PRUint32 aEventType,
+                                      in PRBool aUserCancelled);
 
   /**
    * The number of items being dragged.
@@ -234,4 +236,11 @@ interface nsIDOMNSDataTransfer : nsISupports
    * @throws NS_ERROR_DOM_INDEX_SIZE_ERR if index is greater or equal than itemCount
    */
   nsIVariant mozGetDataAt(in DOMString format, in unsigned long index);
+
+  /**
+   * Will be true if the user cancelled the drag (typically by pressing Escape).
+   * This will be false otherwise, including if a drag failed for any other reason.
+   * This property is only relevant for the dragend event.
+   */
+  readonly attribute boolean mozUserCancelled;
 };
diff --git a/widget/public/nsGUIEvent.h b/widget/public/nsGUIEvent.h
index 094ac2ca5cc..629c84f13ed 100644
--- a/widget/public/nsGUIEvent.h
+++ b/widget/public/nsGUIEvent.h
@@ -775,7 +775,8 @@ class nsDragEvent : public nsMouseEvent
 {
 public:
   nsDragEvent(PRBool isTrusted, PRUint32 msg, nsIWidget *w)
-    : nsMouseEvent(isTrusted, msg, w, NS_DRAG_EVENT, eReal)
+    : nsMouseEvent(isTrusted, msg, w, NS_DRAG_EVENT, eReal),
+      userCancelled(PR_FALSE)
   {
     if (msg == NS_DRAGDROP_EXIT_SYNTH ||
         msg == NS_DRAGDROP_LEAVE_SYNTH ||
@@ -785,6 +786,7 @@ public:
   }
 
   nsCOMPtr<nsIDOMDataTransfer> dataTransfer;
+  PRPackedBool userCancelled;
 };
 
 /**
diff --git a/widget/src/cocoa/nsChildView.mm b/widget/src/cocoa/nsChildView.mm
index 58adf4ed316..c314453bba4 100644
--- a/widget/src/cocoa/nsChildView.mm
+++ b/widget/src/cocoa/nsChildView.mm
@@ -146,6 +146,7 @@ nsIWidget         * gRollupWidget   = nsnull;
 
 PRUint32 gLastModifierState = 0;
 
+PRBool gUserCancelledDrag = PR_FALSE;
 
 @interface ChildView(Private)
 
@@ -6361,6 +6362,10 @@ static BOOL keyUpAlreadySentKeyDown = NO;
 
   gDraggedTransferables = nsnull;
 
+  NSEvent *currentEvent = [NSApp currentEvent];
+  gUserCancelledDrag = ([currentEvent type] == NSKeyDown &&
+                        [currentEvent keyCode] == kEscapeKeyCode);
+
   if (!mDragService) {
     CallGetService(kDragServiceContractID, &mDragService);
     NS_ASSERTION(mDragService, "Couldn't get a drag service - big problem!");
diff --git a/widget/src/cocoa/nsDragService.mm b/widget/src/cocoa/nsDragService.mm
index 78af7778d1b..ab30466470c 100644
--- a/widget/src/cocoa/nsDragService.mm
+++ b/widget/src/cocoa/nsDragService.mm
@@ -78,6 +78,7 @@ extern PRLogModuleInfo* sCocoaLog;
 extern NSPasteboard* globalDragPboard;
 extern NSView* gLastDragView;
 extern NSEvent* gLastDragEvent;
+extern PRBool gUserCancelledDrag;
 
 // This global makes the transferable array available to Cocoa's promised
 // file destination callback.
@@ -308,6 +309,7 @@ nsDragService::InvokeDragSession(nsIDOMNode* aDOMNode, nsISupportsArray* aTransf
   mNativeDragView = [gLastDragView retain];
   mNativeDragEvent = [gLastDragEvent retain];
 
+  gUserCancelledDrag = PR_FALSE;
   [mNativeDragView dragImage:image
                           at:localPoint
                       offset:NSMakeSize(0,0)
@@ -315,6 +317,7 @@ nsDragService::InvokeDragSession(nsIDOMNode* aDOMNode, nsISupportsArray* aTransf
                   pasteboard:[NSPasteboard pasteboardWithName:NSDragPboard]
                       source:mNativeDragView
                    slideBack:YES];
+  gUserCancelledDrag = PR_FALSE;
 
   if (mDoingDrag)
     nsBaseDragService::EndDragSession(PR_FALSE);
@@ -587,6 +590,8 @@ nsDragService::EndDragSession(PRBool aDoneDrag)
     mNativeDragEvent = nil;
   }
 
+  mUserCancelled = gUserCancelledDrag;
+
   nsresult rv = nsBaseDragService::EndDragSession(aDoneDrag);
   mDataItems = nsnull;
   return rv;
diff --git a/widget/src/windows/nsDragService.cpp b/widget/src/windows/nsDragService.cpp
index fd4cd1b1f0c..18de557e1b5 100644
--- a/widget/src/windows/nsDragService.cpp
+++ b/widget/src/windows/nsDragService.cpp
@@ -270,11 +270,12 @@ nsDragService::StartInvokingDragSession(IDataObject * aDataObj,
 {
   // To do the drag we need to create an object that
   // implements the IDataObject interface (for OLE)
-  NS_IF_RELEASE(mNativeDragSrc);
-  mNativeDragSrc = (IDropSource *)new nsNativeDragSource();
-  if (!mNativeDragSrc)
+  nsNativeDragSource* nativeDragSource = new nsNativeDragSource();
+  if (!nativeDragSource)
     return NS_ERROR_OUT_OF_MEMORY;
 
+  NS_IF_RELEASE(mNativeDragSrc);
+  mNativeDragSrc = (IDropSource *)nativeDragSource;
   mNativeDragSrc->AddRef();
 
   // Now figure out what the native drag effect should be
@@ -351,7 +352,9 @@ nsDragService::StartInvokingDragSession(IDataObject * aDataObj,
         dataTransfer->SetDropEffectInt(DRAGDROP_ACTION_NONE);
     }
   }
-      
+
+  mUserCancelled = nativeDragSource->UserCancelled();
+
   // We're done dragging
   EndDragSession(PR_TRUE);
 
diff --git a/widget/src/windows/nsNativeDragSource.cpp b/widget/src/windows/nsNativeDragSource.cpp
index 82a2810c395..46fcfb2caf3 100644
--- a/widget/src/windows/nsNativeDragSource.cpp
+++ b/widget/src/windows/nsNativeDragSource.cpp
@@ -44,7 +44,7 @@
  * class nsNativeDragSource
  */
 nsNativeDragSource::nsNativeDragSource()
-  : m_cRef(0)
+  : m_cRef(0), mUserCancelled(PR_FALSE)
 {
 }
 
@@ -99,6 +99,7 @@ nsNativeDragSource::QueryContinueDrag(BOOL fEsc, DWORD grfKeyState)
 #ifdef DEBUG
     //printf("fEsc\n");
 #endif
+    mUserCancelled = PR_TRUE;
     return ResultFromScode(DRAGDROP_S_CANCEL);
   }
 
diff --git a/widget/src/windows/nsNativeDragSource.h b/widget/src/windows/nsNativeDragSource.h
index 53606b22e5e..e194eb324e6 100644
--- a/widget/src/windows/nsNativeDragSource.h
+++ b/widget/src/windows/nsNativeDragSource.h
@@ -37,6 +37,7 @@
 #ifndef _nsNativeDragSource_h_
 #define _nsNativeDragSource_h_
 
+#include "nscore.h"
 #include <ole2.h>
 #include <oleidl.h>
 
@@ -74,11 +75,13 @@ public:
   // to execute the drop, otherwise NOERROR.
   STDMETHODIMP QueryContinueDrag(BOOL fESC, DWORD grfKeyState);
 
+  PRPackedBool UserCancelled() { return mUserCancelled; }
+
 protected:
   ULONG        m_cRef;     // reference count
-  //nsIDragSource *  mDragSource; // adapter
-  //CfDragDrop *  mDragSource; // adapter
 
+  // true if the user cancelled the drag by pressing escape
+  PRPackedBool mUserCancelled;
 };
 
 #endif // _nsNativeDragSource_h_
diff --git a/widget/src/xpwidgets/nsBaseDragService.cpp b/widget/src/xpwidgets/nsBaseDragService.cpp
index 3f6d6b362fe..2bc38506654 100644
--- a/widget/src/xpwidgets/nsBaseDragService.cpp
+++ b/widget/src/xpwidgets/nsBaseDragService.cpp
@@ -78,7 +78,7 @@
 #define DRAGIMAGES_PREF "nglayout.enable_drag_images"
 
 nsBaseDragService::nsBaseDragService()
-  : mCanDrop(PR_FALSE), mDoingDrag(PR_FALSE), mHasImage(PR_FALSE),
+  : mCanDrop(PR_FALSE), mDoingDrag(PR_FALSE), mHasImage(PR_FALSE), mUserCancelled(PR_FALSE),
     mDragAction(DRAGDROP_ACTION_NONE), mTargetSize(0,0),
     mImageX(0), mImageY(0), mScreenX(-1), mScreenY(-1), mSuppressLevel(0)
 {
@@ -354,6 +354,7 @@ nsBaseDragService::EndDragSession(PRBool aDoneDrag)
   mSelection = nsnull;
   mDataTransfer = nsnull;
   mHasImage = PR_FALSE;
+  mUserCancelled = PR_FALSE;
   mImage = nsnull;
   mImageX = 0;
   mImageY = 0;
@@ -373,6 +374,7 @@ nsBaseDragService::FireDragEventAtSource(PRUint32 aMsg)
       if (presShell) {
         nsEventStatus status = nsEventStatus_eIgnore;
         nsDragEvent event(PR_TRUE, aMsg, nsnull);
+        event.userCancelled = (aMsg == NS_DRAGDROP_END && mUserCancelled);
 
         nsCOMPtr<nsIContent> content = do_QueryInterface(mSourceNode);
         return presShell->HandleDOMEventWithTarget(content, &event, &status);
diff --git a/widget/src/xpwidgets/nsBaseDragService.h b/widget/src/xpwidgets/nsBaseDragService.h
index f17e0655040..1d891ace303 100644
--- a/widget/src/xpwidgets/nsBaseDragService.h
+++ b/widget/src/xpwidgets/nsBaseDragService.h
@@ -129,6 +129,8 @@ protected:
   PRPackedBool mDoingDrag;
   // true if mImage should be used to set a drag image
   PRPackedBool mHasImage;
+  // true if the user cancelled the drag operation
+  PRPackedBool mUserCancelled;
 
   PRUint32 mDragAction;
   nsSize mTargetSize;