Fixed circular references. nsDocLoader now supports weak references to it. Init() method moves out of constructor. nsDocLoader now has Destroy() method to start breakdown process.

docshell/base/nsWebShell.cpp

@@ -1267,6 +1267,7 @@ nsWebShell::Destroy()
 
   // Stop any URLs that are currently being loaded...
   Stop();
+  mDocLoader->Destroy();
 
   SetContainer(nsnull);
   SetObserver(nsnull);