Bug 594222 - Prevent RemoveObservers from being called more than once. r=dougt a=dougt

xpcom/glue/nsCategoryCache.cpp

@@ -44,7 +44,7 @@
 
 nsCategoryObserver::nsCategoryObserver(const char* aCategory,
                                        nsCategoryListener* aListener)
-  : mListener(nsnull), mCategory(aCategory)
+  : mListener(nsnull), mCategory(aCategory), mObserversRemoved(false)
 {
   if (!mHash.Init()) {
     // OOM
@@ -113,6 +113,10 @@ nsCategoryObserver::ListenerDied() {
 
 NS_HIDDEN_(void)
 nsCategoryObserver::RemoveObservers() {
+  if (mObserversRemoved)
+    return;
+
+  mObserversRemoved = true;
   nsCOMPtr<nsIObserverService> obsSvc =
     do_GetService(NS_OBSERVERSERVICE_CONTRACTID);
   if (obsSvc) {

xpcom/glue/nsCategoryCache.h

@@ -78,6 +78,7 @@ class NS_COM_GLUE nsCategoryObserver : public nsIObserver {
     nsDataHashtable<nsCStringHashKey, nsCString> mHash;
     nsCategoryListener*                          mListener;
     nsCString                                    mCategory;
+    bool                                         mObserversRemoved;
 };
 
 /**