diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 02c5b3c87cdd..33eb5ce1da20 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -225,8 +225,7 @@ ContentParent::Init()
     nsCOMPtr<nsIThreadInternal>
             threadInt(do_QueryInterface(NS_GetCurrentThread()));
     if (threadInt) {
-        threadInt->GetObserver(getter_AddRefs(mOldObserver));
-        threadInt->SetObserver(this);
+        threadInt->AddObserver(this);
     }
     if (obs) {
         obs->NotifyObservers(static_cast<nsIObserver*>(this), "ipc:content-created", nsnull);
@@ -344,7 +343,7 @@ ContentParent::ActorDestroy(ActorDestroyReason why)
     nsCOMPtr<nsIThreadInternal>
         threadInt(do_QueryInterface(NS_GetCurrentThread()));
     if (threadInt)
-        threadInt->SetObserver(mOldObserver);
+        threadInt->RemoveObserver(this);
     if (mRunToCompletionDepth)
         mRunToCompletionDepth = 0;
 
@@ -1118,11 +1117,9 @@ ContentParent::RecvLoadURIExternal(const IPC::URI& uri)
 /* void onDispatchedEvent (in nsIThreadInternal thread); */
 NS_IMETHODIMP
 ContentParent::OnDispatchedEvent(nsIThreadInternal *thread)
-{
-    if (mOldObserver)
-        return mOldObserver->OnDispatchedEvent(thread);
-
-    return NS_OK;
+{
+   NS_NOTREACHED("OnDispatchedEvent unimplemented");
+   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 /* void onProcessNextEvent (in nsIThreadInternal thread, in boolean mayWait, in unsigned long recursionDepth); */
@@ -1134,9 +1131,6 @@ ContentParent::OnProcessNextEvent(nsIThreadInternal *thread,
     if (mRunToCompletionDepth)
         ++mRunToCompletionDepth;
 
-    if (mOldObserver)
-        return mOldObserver->OnProcessNextEvent(thread, mayWait, recursionDepth);
-
     return NS_OK;
 }
 
@@ -1156,9 +1150,6 @@ ContentParent::AfterProcessNextEvent(nsIThreadInternal *thread,
             }
     }
 
-    if (mOldObserver)
-        return mOldObserver->AfterProcessNextEvent(thread, recursionDepth);
-
     return NS_OK;
 }
 
diff --git a/dom/ipc/ContentParent.h b/dom/ipc/ContentParent.h
index 2876f987f17e..fed87240a993 100644
--- a/dom/ipc/ContentParent.h
+++ b/dom/ipc/ContentParent.h
@@ -235,7 +235,6 @@ private:
     PRInt32 mGeolocationWatchID;
     int mRunToCompletionDepth;
     bool mShouldCallUnblockChild;
-    nsCOMPtr<nsIThreadObserver> mOldObserver;
 
     // This is a cache of all of the memory reporters
     // registered in the child process.  To update this, one