diff --git a/mozilla/xpcom/src/Makefile.in b/mozilla/xpcom/src/Makefile.in
index 520c3d3d599..2014c56b8ad 100644
--- a/mozilla/xpcom/src/Makefile.in
+++ b/mozilla/xpcom/src/Makefile.in
@@ -44,6 +44,7 @@ CPPSRCS		= \
 	nsXPComFactory.cpp \
 	nsXPIDLString.cpp \
 	nsEventQueueService.cpp \
+	nsEventQueue.cpp \
 	xcDll.cpp \
 	nsAllocator.cpp \
 	nsGenericFactory.cpp \
diff --git a/mozilla/xpcom/src/makefile.win b/mozilla/xpcom/src/makefile.win
index ecdb90736f9..5bf6c0dad5c 100644
--- a/mozilla/xpcom/src/makefile.win
+++ b/mozilla/xpcom/src/makefile.win
@@ -70,6 +70,7 @@ CPPSRCS =                             \
         nsXPComFactory.cpp            \
         nsXPIDLString.cpp             \
         nsEventQueueService.cpp       \
+		nsEventQueue.cpp			  \
         nsAllocator.cpp               \
         xcDll.cpp                     \
         nsGenericFactory.cpp          \
@@ -93,6 +94,7 @@ CPP_OBJS =                                        \
         .\$(OBJDIR)\nsXPComFactory.obj            \
         .\$(OBJDIR)\nsXPIDLString.obj             \
         .\$(OBJDIR)\nsEventQueueService.obj       \
+		.\$(OBJDIR)\nsEventQueue.obj			  \
         .\$(OBJDIR)\nsAllocator.obj               \
         .\$(OBJDIR)\xcDll.obj                     \
         .\$(OBJDIR)\nsGenericFactory.obj          \
diff --git a/mozilla/xpcom/src/nsEventQueue.cpp b/mozilla/xpcom/src/nsEventQueue.cpp
new file mode 100644
index 00000000000..99c3aeb7324
--- /dev/null
+++ b/mozilla/xpcom/src/nsEventQueue.cpp
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is Netscape Communications
+ * Corporation.  Portions created by Netscape are Copyright (C) 1998
+ * Netscape Communications Corporation.  All Rights Reserved.
+ */
+
+#include "nsEventQueue.h"
+
+nsEventQueueImpl::nsEventQueueImpl()
+{
+  NS_INIT_REFCNT();
+
+  mEventQueue = NULL;
+	
+}
+
+nsEventQueueImpl::~nsEventQueueImpl()
+{
+  if (NULL != mEventQueue) {
+    PL_DestroyEventQueue(mEventQueue);
+  }
+}
+
+NS_IMETHODIMP 
+nsEventQueueImpl::Init()
+{
+  mEventQueue = PL_CreateNativeEventQueue("Thread event queue...", PR_GetCurrentThread());
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::InitFromPLQueue(PLEventQueue* aQueue)
+{
+	mEventQueue = aQueue;
+	return NS_OK;
+}
+
+/* nsISupports interface implementation... */
+NS_IMPL_ISUPPORTS(nsEventQueueImpl,kIEventQueueIID);
+
+/* nsIEventQueue interface implementation... */
+
+NS_IMETHODIMP_(PRStatus)
+nsEventQueueImpl::PostEvent(PLEvent* aEvent)
+{
+	return PL_PostEvent(mEventQueue, aEvent);
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::PostSynchronousEvent(PLEvent* aEvent)
+{
+	PL_PostSynchronousEvent(mEventQueue, aEvent);
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::ProcessPendingEvents()
+{
+	PL_ProcessPendingEvents(mEventQueue);
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::EventAvailable(PRBool& aResult)
+{
+	aResult = PL_EventAvailable(mEventQueue);
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::GetEvent(PLEvent** aResult)
+{
+	*aResult = PL_GetEvent(mEventQueue);
+	return NS_OK;
+}
+
+NS_IMETHODIMP_(PRInt32) 
+nsEventQueueImpl::GetEventQueueSelectFD() 
+{
+  return PL_GetEventQueueSelectFD(mEventQueue);
+}
+
+NS_METHOD
+nsEventQueueImpl::Create(nsISupports *aOuter,
+                            REFNSIID aIID,
+                            void **aResult)
+{
+  nsEventQueueImpl* evt = new nsEventQueueImpl();
+  if (evt == NULL)
+    return NS_ERROR_OUT_OF_MEMORY;
+  nsresult rv = evt->QueryInterface(aIID, aResult);
+  return rv;
+}
diff --git a/mozilla/xpcom/src/nsEventQueue.h b/mozilla/xpcom/src/nsEventQueue.h
new file mode 100644
index 00000000000..8c323013302
--- /dev/null
+++ b/mozilla/xpcom/src/nsEventQueue.h
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is Netscape Communications
+ * Corporation.  Portions created by Netscape are Copyright (C) 1998
+ * Netscape Communications Corporation.  All Rights Reserved.
+ */
+
+#include "prmon.h"
+#include "nsIEventQueue.h"
+#include "nsXPComFactory.h"
+
+static NS_DEFINE_IID(kIEventQueueIID, NS_IEVENTQUEUE_IID);
+
+class nsEventQueueImpl : public nsIEventQueue
+{
+public:
+  nsEventQueueImpl();
+
+  // nsISupports interface...
+  NS_DECL_ISUPPORTS
+
+  // nsIEventQueue interface...
+	NS_IMETHOD_(PRStatus) PostEvent(PLEvent* aEvent);
+	NS_IMETHOD PostSynchronousEvent(PLEvent* aEvent);
+  NS_IMETHOD ProcessPendingEvents();
+	NS_IMETHOD EventAvailable(PRBool& aResult);
+	NS_IMETHOD GetEvent(PLEvent** aResult);
+
+  NS_IMETHOD_(PRInt32) GetEventQueueSelectFD();
+
+	NS_IMETHOD Init();
+	NS_IMETHOD InitFromPLQueue(PLEventQueue* aQueue);
+
+	// Helpers
+	static NS_METHOD
+  Create(nsISupports* outer, const nsIID& aIID, void* *aInstancePtr);
+
+	static const nsCID& CID() { static nsCID cid = NS_EVENTQUEUE_CID; return cid; }
+
+protected:
+  ~nsEventQueueImpl();
+
+private:
+  PLEventQueue*	mEventQueue;
+};
+
+
+
diff --git a/mozilla/xpcom/src/nsEventQueueService.cpp b/mozilla/xpcom/src/nsEventQueueService.cpp
index c4c2cdc82c3..63c40524f28 100644
--- a/mozilla/xpcom/src/nsEventQueueService.cpp
+++ b/mozilla/xpcom/src/nsEventQueueService.cpp
@@ -17,15 +17,14 @@
  * Netscape Communications Corporation.  All Rights Reserved.
  */
 #include "prmon.h"
+#include "nsComponentManager.h"
 #include "nsIEventQueueService.h"
+#include "nsIEventQueue.h"
 #include "nsHashtable.h"
 #include "nsXPComFactory.h"
 
-
 static NS_DEFINE_IID(kIEventQueueServiceIID, NS_IEVENTQUEUESERVICE_IID);
 
-
-
 // XXX move to nsID.h or nsHashtable.h? (copied from nsComponentManager.cpp)
 class ThreadKey: public nsHashKey {
 private:
@@ -50,6 +49,66 @@ public:
 };
 
 
+/* This class is used with the EventQueueEntries to allow us to nest
+   event queues */
+class EventQueueStack
+{
+public:
+	EventQueueStack(EventQueueStack* next = NULL);
+	~EventQueueStack();
+
+	nsIEventQueue* GetEventQueue();
+	EventQueueStack* GetNext();
+  void SetNext(EventQueueStack* aStack);
+
+private:
+	nsIEventQueue* mEventQueue;
+	EventQueueStack* mNextQueue;
+};
+
+static NS_DEFINE_IID(kIEventQueueIID, NS_IEVENTQUEUE_IID);
+static NS_DEFINE_IID(kEventQueueCID, NS_EVENTQUEUE_CID);
+
+EventQueueStack::EventQueueStack(EventQueueStack* next)
+:mNextQueue(next)
+{
+  // Create our thread queue using the component manager
+	if (NS_FAILED(nsComponentManager::CreateInstance(kEventQueueCID, NULL, kIEventQueueIID,
+		(void**)&mEventQueue))) {
+		mEventQueue = NULL;
+	}
+
+	if (NS_FAILED(mEventQueue->Init()))
+		mEventQueue = NULL;
+}
+
+EventQueueStack::~EventQueueStack()
+{
+	// Destroy our thread queue.
+	NS_IF_RELEASE(mEventQueue);
+
+	if (mNextQueue)
+	{
+		delete mNextQueue;
+	}
+}
+
+nsIEventQueue* EventQueueStack::GetEventQueue()
+{
+	NS_ADDREF(mEventQueue);
+	return mEventQueue;
+}
+
+EventQueueStack* EventQueueStack::GetNext()
+{
+	return mNextQueue;
+}
+
+void EventQueueStack::SetNext(EventQueueStack* aStack)
+{
+	mNextQueue = aStack;
+}
+
 /*
  * This class maintains the data associated with each entry in the EventQueue
  * service's hash table...
@@ -66,10 +125,13 @@ public:
   // nsISupports interface...
   NS_DECL_ISUPPORTS
 
-  PLEventQueue* GetEventQueue(void);
+  nsIEventQueue* GetEventQueue(void);
+  
+	void PushQueue(void);
+  void PopQueue(void);
 
 private: 
-  PLEventQueue* mEventQueue; 
+	EventQueueStack* mQueueStack;
 };
 
 /* nsISupports interface implementation... */
@@ -79,22 +141,42 @@ EventQueueEntry::EventQueueEntry()
 {
   NS_INIT_REFCNT();
 
-  mEventQueue = PL_CreateNativeEventQueue("Thread event queue...", PR_GetCurrentThread());
+	mQueueStack = new EventQueueStack();
 }
 
 EventQueueEntry::~EventQueueEntry()
 {
-  if (NULL != mEventQueue) {
-    PL_DestroyEventQueue(mEventQueue);
-  }
+  // Delete our stack
+	delete mQueueStack;
 }
 
-PLEventQueue* EventQueueEntry::GetEventQueue(void)
+nsIEventQueue* EventQueueEntry::GetEventQueue(void)
 {
-  return mEventQueue;
+	// Return the current event queue on our stack.
+  nsIEventQueue* answer = NULL;
+	if (mQueueStack)
+		answer = mQueueStack->GetEventQueue(); // This call addrefs the queue
+	return answer;
 }
 
+void EventQueueEntry::PushQueue(void)
+{
+	// Make a new thread queue, connect it to our current stack, and then
+	// set it to be the top of our stack.
+	mQueueStack = new EventQueueStack(mQueueStack);
+}
 
+void EventQueueEntry::PopQueue(void)
+{
+	EventQueueStack* popped = mQueueStack;
+	if (mQueueStack) {
+		mQueueStack = mQueueStack->GetNext();
+		popped->SetNext(NULL);
+	}
+
+	// This will result in the queue being released.
+	delete popped;
+}
 
 class nsEventQueueServiceImpl : public nsIEventQueueService
 {
@@ -107,7 +189,12 @@ public:
   // nsIEventQueueService interface...
   NS_IMETHOD CreateThreadEventQueue(void);
   NS_IMETHOD DestroyThreadEventQueue(void);
-  NS_IMETHOD GetThreadEventQueue(PRThread* aThread, PLEventQueue** aResult);
+  NS_IMETHOD GetThreadEventQueue(PRThread* aThread, nsIEventQueue** aResult);
+
+	NS_IMETHOD CreateFromPLEventQueue(PLEventQueue* aPLEventQueue, nsIEventQueue** aResult);
+
+	NS_IMETHOD PushThreadEventQueue(void);
+	NS_IMETHOD PopThreadEventQueue(void);
 
 #ifdef XP_MAC
   NS_IMETHOD ProcessEvents();
@@ -211,9 +298,94 @@ nsEventQueueServiceImpl::DestroyThreadEventQueue(void)
   return rv;
 }
 
+NS_IMETHODIMP
+nsEventQueueServiceImpl::CreateFromPLEventQueue(PLEventQueue* aPLEventQueue, nsIEventQueue** aResult)
+{
+	// Create our thread queue using the component manager
+	nsresult rv;
+	nsIEventQueue* aQueue;
+	if (NS_FAILED(rv = nsComponentManager::CreateInstance(kEventQueueCID, NULL, kIEventQueueIID,
+		            (void**)&aQueue))) {
+		return rv;
+	}
+
+	if (NS_FAILED(rv = aQueue->InitFromPLQueue(aPLEventQueue))) {
+		NS_IF_RELEASE(aQueue);
+		return rv;
+	}
+
+	*aResult = aQueue;
+	return NS_OK;
+}
 
 NS_IMETHODIMP
-nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, PLEventQueue** aResult)
+nsEventQueueServiceImpl::PushThreadEventQueue()
+{
+	nsresult rv = NS_OK;
+  ThreadKey  key(PR_GetCurrentThread());
+  EventQueueEntry* evQueueEntry;
+
+  /* Enter the lock which protects the EventQ hashtable... */
+  PR_EnterMonitor(mEventQMonitor);
+
+  /* Only create one event queue per thread... */
+  evQueueEntry = (EventQueueEntry*)mEventQTable->Get(&key);
+  if (NULL == evQueueEntry) {
+    evQueueEntry = new EventQueueEntry();  
+    if (NULL == evQueueEntry) {
+      rv = NS_ERROR_OUT_OF_MEMORY;
+      goto done;
+    }
+    mEventQTable->Put(&key, evQueueEntry);
+  }
+	else {
+			// An entry was already present. We need to push a new
+			// queue onto our stack.
+			evQueueEntry->PushQueue();
+	}
+
+  NS_ADDREF(evQueueEntry);
+
+done:
+  // Release the EventQ lock...
+  PR_ExitMonitor(mEventQMonitor);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsEventQueueServiceImpl::PopThreadEventQueue(void)
+{
+  nsresult rv = NS_OK;
+  ThreadKey key(PR_GetCurrentThread());
+  EventQueueEntry* evQueueEntry;
+
+  /* Enter the lock which protects the EventQ hashtable... */
+  PR_EnterMonitor(mEventQMonitor);
+
+  evQueueEntry = (EventQueueEntry*)mEventQTable->Get(&key);
+  if (NULL != evQueueEntry) {
+    nsrefcnt refcnt;
+
+    NS_RELEASE2(evQueueEntry, refcnt);
+    // Remove the entry from the hash table if this was the last reference...
+    if (0 == refcnt) {
+      mEventQTable->Remove(&key);
+    }
+		else {
+			// We must be popping.
+			evQueueEntry->PopQueue();
+		}
+  } else {
+    rv = NS_ERROR_FAILURE;
+  }
+
+  // Release the EventQ lock...
+  PR_ExitMonitor(mEventQMonitor);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, nsIEventQueue** aResult)
 {
   nsresult rv = NS_OK;
   EventQueueEntry* evQueueEntry;
@@ -230,7 +402,7 @@ nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, PLEventQueue** a
 
   evQueueEntry = (EventQueueEntry*)mEventQTable->Get(&key);
   if (NULL != evQueueEntry) {
-    *aResult = evQueueEntry->GetEventQueue();
+    *aResult = evQueueEntry->GetEventQueue(); // Queue addrefing is done by this call.
   } else {
     // XXX: Need error code for requesting an event queue when none exists...
     *aResult = NULL;
@@ -248,7 +420,13 @@ done:
 static  PRBool EventDispatchingFunc(nsHashKey *aKey, void *aData, void* closure)
 {
 	EventQueueEntry* entry = (EventQueueEntry*) aData;
-	PL_ProcessPendingEvents( entry->GetEventQueue() );
+	nsIEventQueue* eventQueue = entry->GetEventQueue();
+	
+	if (eventQueue) {
+		eventQueue->ProcessPendingEvents();
+		NS_RELEASE(eventQueue);
+	}
+
 	return true;
 }
 
diff --git a/mozilla/xpcom/src/nsXPComFactory.cpp b/mozilla/xpcom/src/nsXPComFactory.cpp
index 3435476fca1..843dfadefe9 100644
--- a/mozilla/xpcom/src/nsXPComFactory.cpp
+++ b/mozilla/xpcom/src/nsXPComFactory.cpp
@@ -19,6 +19,7 @@
 #include "nsXPComFactory.h"
 #include "nsXPComCIID.h"
 #include "nsAllocator.h"
+#include "nsEventQueue.h"
 #include "nsGenericFactory.h"
 
 static NS_DEFINE_IID(kEventQueueServiceCID, NS_EVENTQUEUESERVICE_CID);
@@ -56,6 +57,8 @@ NSGetFactory(nsISupports* serviceMgr,
 		nsGenericFactory* factory = NULL;
 		if (aClass.Equals(nsAllocatorImpl::CID())) {
 			factory = new nsGenericFactory(&nsAllocatorImpl::Create);
+		} else if (aClass.Equals(nsEventQueueImpl::CID())) {
+			factory = new nsGenericFactory(&nsEventQueueImpl::Create);
 		} else if (aClass.Equals(nsGenericFactory::CID())) {
 			// whoa, create a generic factory that creates generic factories!
 			factory = new nsGenericFactory(&nsGenericFactory::Create);
diff --git a/mozilla/xpcom/threads/nsEventQueue.cpp b/mozilla/xpcom/threads/nsEventQueue.cpp
new file mode 100644
index 00000000000..99c3aeb7324
--- /dev/null
+++ b/mozilla/xpcom/threads/nsEventQueue.cpp
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is Netscape Communications
+ * Corporation.  Portions created by Netscape are Copyright (C) 1998
+ * Netscape Communications Corporation.  All Rights Reserved.
+ */
+
+#include "nsEventQueue.h"
+
+nsEventQueueImpl::nsEventQueueImpl()
+{
+  NS_INIT_REFCNT();
+
+  mEventQueue = NULL;
+	
+}
+
+nsEventQueueImpl::~nsEventQueueImpl()
+{
+  if (NULL != mEventQueue) {
+    PL_DestroyEventQueue(mEventQueue);
+  }
+}
+
+NS_IMETHODIMP 
+nsEventQueueImpl::Init()
+{
+  mEventQueue = PL_CreateNativeEventQueue("Thread event queue...", PR_GetCurrentThread());
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::InitFromPLQueue(PLEventQueue* aQueue)
+{
+	mEventQueue = aQueue;
+	return NS_OK;
+}
+
+/* nsISupports interface implementation... */
+NS_IMPL_ISUPPORTS(nsEventQueueImpl,kIEventQueueIID);
+
+/* nsIEventQueue interface implementation... */
+
+NS_IMETHODIMP_(PRStatus)
+nsEventQueueImpl::PostEvent(PLEvent* aEvent)
+{
+	return PL_PostEvent(mEventQueue, aEvent);
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::PostSynchronousEvent(PLEvent* aEvent)
+{
+	PL_PostSynchronousEvent(mEventQueue, aEvent);
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::ProcessPendingEvents()
+{
+	PL_ProcessPendingEvents(mEventQueue);
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::EventAvailable(PRBool& aResult)
+{
+	aResult = PL_EventAvailable(mEventQueue);
+	return NS_OK;
+}
+
+NS_IMETHODIMP
+nsEventQueueImpl::GetEvent(PLEvent** aResult)
+{
+	*aResult = PL_GetEvent(mEventQueue);
+	return NS_OK;
+}
+
+NS_IMETHODIMP_(PRInt32) 
+nsEventQueueImpl::GetEventQueueSelectFD() 
+{
+  return PL_GetEventQueueSelectFD(mEventQueue);
+}
+
+NS_METHOD
+nsEventQueueImpl::Create(nsISupports *aOuter,
+                            REFNSIID aIID,
+                            void **aResult)
+{
+  nsEventQueueImpl* evt = new nsEventQueueImpl();
+  if (evt == NULL)
+    return NS_ERROR_OUT_OF_MEMORY;
+  nsresult rv = evt->QueryInterface(aIID, aResult);
+  return rv;
+}
diff --git a/mozilla/xpcom/threads/nsEventQueue.h b/mozilla/xpcom/threads/nsEventQueue.h
new file mode 100644
index 00000000000..8c323013302
--- /dev/null
+++ b/mozilla/xpcom/threads/nsEventQueue.h
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is Netscape Communications
+ * Corporation.  Portions created by Netscape are Copyright (C) 1998
+ * Netscape Communications Corporation.  All Rights Reserved.
+ */
+
+#include "prmon.h"
+#include "nsIEventQueue.h"
+#include "nsXPComFactory.h"
+
+static NS_DEFINE_IID(kIEventQueueIID, NS_IEVENTQUEUE_IID);
+
+class nsEventQueueImpl : public nsIEventQueue
+{
+public:
+  nsEventQueueImpl();
+
+  // nsISupports interface...
+  NS_DECL_ISUPPORTS
+
+  // nsIEventQueue interface...
+	NS_IMETHOD_(PRStatus) PostEvent(PLEvent* aEvent);
+	NS_IMETHOD PostSynchronousEvent(PLEvent* aEvent);
+  NS_IMETHOD ProcessPendingEvents();
+	NS_IMETHOD EventAvailable(PRBool& aResult);
+	NS_IMETHOD GetEvent(PLEvent** aResult);
+
+  NS_IMETHOD_(PRInt32) GetEventQueueSelectFD();
+
+	NS_IMETHOD Init();
+	NS_IMETHOD InitFromPLQueue(PLEventQueue* aQueue);
+
+	// Helpers
+	static NS_METHOD
+  Create(nsISupports* outer, const nsIID& aIID, void* *aInstancePtr);
+
+	static const nsCID& CID() { static nsCID cid = NS_EVENTQUEUE_CID; return cid; }
+
+protected:
+  ~nsEventQueueImpl();
+
+private:
+  PLEventQueue*	mEventQueue;
+};
+
+
+
diff --git a/mozilla/xpcom/threads/nsEventQueueService.cpp b/mozilla/xpcom/threads/nsEventQueueService.cpp
index c4c2cdc82c3..63c40524f28 100644
--- a/mozilla/xpcom/threads/nsEventQueueService.cpp
+++ b/mozilla/xpcom/threads/nsEventQueueService.cpp
@@ -17,15 +17,14 @@
  * Netscape Communications Corporation.  All Rights Reserved.
  */
 #include "prmon.h"
+#include "nsComponentManager.h"
 #include "nsIEventQueueService.h"
+#include "nsIEventQueue.h"
 #include "nsHashtable.h"
 #include "nsXPComFactory.h"
 
-
 static NS_DEFINE_IID(kIEventQueueServiceIID, NS_IEVENTQUEUESERVICE_IID);
 
-
-
 // XXX move to nsID.h or nsHashtable.h? (copied from nsComponentManager.cpp)
 class ThreadKey: public nsHashKey {
 private:
@@ -50,6 +49,66 @@ public:
 };
 
 
+/* This class is used with the EventQueueEntries to allow us to nest
+   event queues */
+class EventQueueStack
+{
+public:
+	EventQueueStack(EventQueueStack* next = NULL);
+	~EventQueueStack();
+
+	nsIEventQueue* GetEventQueue();
+	EventQueueStack* GetNext();
+  void SetNext(EventQueueStack* aStack);
+
+private:
+	nsIEventQueue* mEventQueue;
+	EventQueueStack* mNextQueue;
+};
+
+static NS_DEFINE_IID(kIEventQueueIID, NS_IEVENTQUEUE_IID);
+static NS_DEFINE_IID(kEventQueueCID, NS_EVENTQUEUE_CID);
+
+EventQueueStack::EventQueueStack(EventQueueStack* next)
+:mNextQueue(next)
+{
+  // Create our thread queue using the component manager
+	if (NS_FAILED(nsComponentManager::CreateInstance(kEventQueueCID, NULL, kIEventQueueIID,
+		(void**)&mEventQueue))) {
+		mEventQueue = NULL;
+	}
+
+	if (NS_FAILED(mEventQueue->Init()))
+		mEventQueue = NULL;
+}
+
+EventQueueStack::~EventQueueStack()
+{
+	// Destroy our thread queue.
+	NS_IF_RELEASE(mEventQueue);
+
+	if (mNextQueue)
+	{
+		delete mNextQueue;
+	}
+}
+
+nsIEventQueue* EventQueueStack::GetEventQueue()
+{
+	NS_ADDREF(mEventQueue);
+	return mEventQueue;
+}
+
+EventQueueStack* EventQueueStack::GetNext()
+{
+	return mNextQueue;
+}
+
+void EventQueueStack::SetNext(EventQueueStack* aStack)
+{
+	mNextQueue = aStack;
+}
+
 /*
  * This class maintains the data associated with each entry in the EventQueue
  * service's hash table...
@@ -66,10 +125,13 @@ public:
   // nsISupports interface...
   NS_DECL_ISUPPORTS
 
-  PLEventQueue* GetEventQueue(void);
+  nsIEventQueue* GetEventQueue(void);
+  
+	void PushQueue(void);
+  void PopQueue(void);
 
 private: 
-  PLEventQueue* mEventQueue; 
+	EventQueueStack* mQueueStack;
 };
 
 /* nsISupports interface implementation... */
@@ -79,22 +141,42 @@ EventQueueEntry::EventQueueEntry()
 {
   NS_INIT_REFCNT();
 
-  mEventQueue = PL_CreateNativeEventQueue("Thread event queue...", PR_GetCurrentThread());
+	mQueueStack = new EventQueueStack();
 }
 
 EventQueueEntry::~EventQueueEntry()
 {
-  if (NULL != mEventQueue) {
-    PL_DestroyEventQueue(mEventQueue);
-  }
+  // Delete our stack
+	delete mQueueStack;
 }
 
-PLEventQueue* EventQueueEntry::GetEventQueue(void)
+nsIEventQueue* EventQueueEntry::GetEventQueue(void)
 {
-  return mEventQueue;
+	// Return the current event queue on our stack.
+  nsIEventQueue* answer = NULL;
+	if (mQueueStack)
+		answer = mQueueStack->GetEventQueue(); // This call addrefs the queue
+	return answer;
 }
 
+void EventQueueEntry::PushQueue(void)
+{
+	// Make a new thread queue, connect it to our current stack, and then
+	// set it to be the top of our stack.
+	mQueueStack = new EventQueueStack(mQueueStack);
+}
 
+void EventQueueEntry::PopQueue(void)
+{
+	EventQueueStack* popped = mQueueStack;
+	if (mQueueStack) {
+		mQueueStack = mQueueStack->GetNext();
+		popped->SetNext(NULL);
+	}
+
+	// This will result in the queue being released.
+	delete popped;
+}
 
 class nsEventQueueServiceImpl : public nsIEventQueueService
 {
@@ -107,7 +189,12 @@ public:
   // nsIEventQueueService interface...
   NS_IMETHOD CreateThreadEventQueue(void);
   NS_IMETHOD DestroyThreadEventQueue(void);
-  NS_IMETHOD GetThreadEventQueue(PRThread* aThread, PLEventQueue** aResult);
+  NS_IMETHOD GetThreadEventQueue(PRThread* aThread, nsIEventQueue** aResult);
+
+	NS_IMETHOD CreateFromPLEventQueue(PLEventQueue* aPLEventQueue, nsIEventQueue** aResult);
+
+	NS_IMETHOD PushThreadEventQueue(void);
+	NS_IMETHOD PopThreadEventQueue(void);
 
 #ifdef XP_MAC
   NS_IMETHOD ProcessEvents();
@@ -211,9 +298,94 @@ nsEventQueueServiceImpl::DestroyThreadEventQueue(void)
   return rv;
 }
 
+NS_IMETHODIMP
+nsEventQueueServiceImpl::CreateFromPLEventQueue(PLEventQueue* aPLEventQueue, nsIEventQueue** aResult)
+{
+	// Create our thread queue using the component manager
+	nsresult rv;
+	nsIEventQueue* aQueue;
+	if (NS_FAILED(rv = nsComponentManager::CreateInstance(kEventQueueCID, NULL, kIEventQueueIID,
+		            (void**)&aQueue))) {
+		return rv;
+	}
+
+	if (NS_FAILED(rv = aQueue->InitFromPLQueue(aPLEventQueue))) {
+		NS_IF_RELEASE(aQueue);
+		return rv;
+	}
+
+	*aResult = aQueue;
+	return NS_OK;
+}
 
 NS_IMETHODIMP
-nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, PLEventQueue** aResult)
+nsEventQueueServiceImpl::PushThreadEventQueue()
+{
+	nsresult rv = NS_OK;
+  ThreadKey  key(PR_GetCurrentThread());
+  EventQueueEntry* evQueueEntry;
+
+  /* Enter the lock which protects the EventQ hashtable... */
+  PR_EnterMonitor(mEventQMonitor);
+
+  /* Only create one event queue per thread... */
+  evQueueEntry = (EventQueueEntry*)mEventQTable->Get(&key);
+  if (NULL == evQueueEntry) {
+    evQueueEntry = new EventQueueEntry();  
+    if (NULL == evQueueEntry) {
+      rv = NS_ERROR_OUT_OF_MEMORY;
+      goto done;
+    }
+    mEventQTable->Put(&key, evQueueEntry);
+  }
+	else {
+			// An entry was already present. We need to push a new
+			// queue onto our stack.
+			evQueueEntry->PushQueue();
+	}
+
+  NS_ADDREF(evQueueEntry);
+
+done:
+  // Release the EventQ lock...
+  PR_ExitMonitor(mEventQMonitor);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsEventQueueServiceImpl::PopThreadEventQueue(void)
+{
+  nsresult rv = NS_OK;
+  ThreadKey key(PR_GetCurrentThread());
+  EventQueueEntry* evQueueEntry;
+
+  /* Enter the lock which protects the EventQ hashtable... */
+  PR_EnterMonitor(mEventQMonitor);
+
+  evQueueEntry = (EventQueueEntry*)mEventQTable->Get(&key);
+  if (NULL != evQueueEntry) {
+    nsrefcnt refcnt;
+
+    NS_RELEASE2(evQueueEntry, refcnt);
+    // Remove the entry from the hash table if this was the last reference...
+    if (0 == refcnt) {
+      mEventQTable->Remove(&key);
+    }
+		else {
+			// We must be popping.
+			evQueueEntry->PopQueue();
+		}
+  } else {
+    rv = NS_ERROR_FAILURE;
+  }
+
+  // Release the EventQ lock...
+  PR_ExitMonitor(mEventQMonitor);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, nsIEventQueue** aResult)
 {
   nsresult rv = NS_OK;
   EventQueueEntry* evQueueEntry;
@@ -230,7 +402,7 @@ nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, PLEventQueue** a
 
   evQueueEntry = (EventQueueEntry*)mEventQTable->Get(&key);
   if (NULL != evQueueEntry) {
-    *aResult = evQueueEntry->GetEventQueue();
+    *aResult = evQueueEntry->GetEventQueue(); // Queue addrefing is done by this call.
   } else {
     // XXX: Need error code for requesting an event queue when none exists...
     *aResult = NULL;
@@ -248,7 +420,13 @@ done:
 static  PRBool EventDispatchingFunc(nsHashKey *aKey, void *aData, void* closure)
 {
 	EventQueueEntry* entry = (EventQueueEntry*) aData;
-	PL_ProcessPendingEvents( entry->GetEventQueue() );
+	nsIEventQueue* eventQueue = entry->GetEventQueue();
+	
+	if (eventQueue) {
+		eventQueue->ProcessPendingEvents();
+		NS_RELEASE(eventQueue);
+	}
+
 	return true;
 }