bug 385086: null references to XPCOM components from the content pref service on shutdown so we don't leak them

r=sayrer

toolkit/components/contentprefs/src/nsContentPrefService.js

@@ -81,8 +81,25 @@ ContentPrefService.prototype = {
   _destroy: function ContentPrefService__destroy() {
     this._observerSvc.removeObserver(this, "xpcom-shutdown");
 
-    // mozStorage shuts down the database for us automatically, but this
-    // helps us avoid the appearance of leaking the connection.
+    // Delete various references to XPCOM components so we don't leak them.
+    this.__observerSvc = null;
+    this.__consoleSvc = null;
+    this._grouper = null;
+    this.__stmtSelectPref = null;
+    this.__stmtSelectGlobalPref = null;
+    this.__stmtSelectGroupID = null;
+    this.__stmtInsertGroup = null;
+    this.__stmtSelectSettingID = null;
+    this.__stmtInsertSetting = null;
+    this.__stmtSelectPrefID = null;
+    this.__stmtSelectGlobalPrefID = null;
+    this.__stmtInsertPref = null;
+    this.__stmtUpdatePref = null;
+    this.__stmtDeletePref = null;
+    this.__stmtDeleteSettingIfUnused = null;
+    this.__stmtDeleteGroupIfUnused = null;
+    this.__stmtSelectPrefs = null;
+    this.__stmtSelectGlobalPrefs = null;
     this._dbConnection = null;
   },