--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -3083,18 +3083,16 @@ Preferences::ReadUserPrefsFromFile(nsIFi
   return openPrefFile(aFile);
 }
 
 NS_IMETHODIMP
 Preferences::ResetPrefs()
 {
   ENSURE_PARENT_PROCESS("Preferences::ResetPrefs", "all prefs");
 
-  NotifyServiceObservers(NS_PREFSERVICE_RESET_TOPIC_ID);
-
   gHashTable->ClearAndPrepareForLength(PREF_HASHTABLE_INITIAL_LENGTH);
   gPrefNameArena.Clear();
 
   return InitInitialObjects().isOk() ? NS_OK : NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 Preferences::ResetUserPrefs()

--- a/modules/libpref/nsIPrefService.idl
+++ b/modules/libpref/nsIPrefService.idl
@@ -126,20 +126,14 @@ interface nsIPrefService : nsISupports
 #define NS_PREFSERVICE_CONTRACTID "@mozilla.org/preferences-service;1"
 
 /**
  * Notification sent before reading the default user preferences files.
  */
 #define NS_PREFSERVICE_READ_TOPIC_ID "prefservice:before-read-userprefs"
 
 /**
- * Notification sent when resetPrefs has been called, but before the actual
- * reset process occurs.
- */
-#define NS_PREFSERVICE_RESET_TOPIC_ID "prefservice:before-reset"
-
-/**
  * Notification sent when after reading app-provided default
  * preferences, but before user profile override defaults are loaded.
  */
 #define NS_PREFSERVICE_APPDEFAULTS_TOPIC_ID "prefservice:after-app-defaults"
 
 %}