diff --git a/mozilla/xpcom/threads/nsEventQueue.cpp b/mozilla/xpcom/threads/nsEventQueue.cpp
index 6dac31b8f5a..b1ef3715e6e 100644
--- a/mozilla/xpcom/threads/nsEventQueue.cpp
+++ b/mozilla/xpcom/threads/nsEventQueue.cpp
@@ -104,6 +104,13 @@ nsEventQueueImpl::GetPLEventQueue(PLEventQueue** aEventQueue)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsEventQueueImpl::IsQueueOnCurrentThread(PRBool *aResult)
+{
+    *aResult = PL_IsQueueOnCurrentThread( mEventQueue );
+    return NS_OK;
+}
+
 
 NS_IMETHODIMP
 nsEventQueueImpl::ProcessPendingEvents()
diff --git a/mozilla/xpcom/threads/nsEventQueue.h b/mozilla/xpcom/threads/nsEventQueue.h
index 3260b5b02a9..0e798682c81 100644
--- a/mozilla/xpcom/threads/nsEventQueue.h
+++ b/mozilla/xpcom/threads/nsEventQueue.h
@@ -53,6 +53,8 @@ public:
     NS_IMETHOD RevokeEvents(void* owner);
 
     NS_IMETHOD GetPLEventQueue(PLEventQueue** aEventQueue);
+    
+    NS_IMETHOD IsQueueOnCurrentThread(PRBool *aResult);
 
 	// Helpers
 	static NS_METHOD Create(nsISupports* outer, const nsIID& aIID, void* *aInstancePtr);
diff --git a/mozilla/xpcom/threads/nsIEventQueue.h b/mozilla/xpcom/threads/nsIEventQueue.h
index ea080d282e5..256634d84fb 100644
--- a/mozilla/xpcom/threads/nsIEventQueue.h
+++ b/mozilla/xpcom/threads/nsIEventQueue.h
@@ -60,6 +60,8 @@ public:
 
     NS_IMETHOD RevokeEvents(void* owner) = 0;
     NS_IMETHOD GetPLEventQueue(PLEventQueue** aEventQueue) = 0;
+
+    NS_IMETHOD IsQueueOnCurrentThread(PRBool *aResult) = 0;
 };
 
 #endif /* nsIEventQueue_h___ */