Bug 1626728 - Normalize shutdown. r=perry, a=RyanVM

Differential Revision: https://phabricator.services.mozilla.com/D69463

--HG--
extra : amend_source : 9f957a6cc3c3e767be73fadf428e8e7c3322d5ae

dom/cache/StreamList.cpp

@@ -133,7 +133,10 @@ void StreamList::Close(const nsID& aId) {
 void StreamList::CloseAll() {
   NS_ASSERT_OWNINGTHREAD(StreamList);
   if (mStreamControl) {
-    mStreamControl->CloseAll();
+    auto streamControl = mStreamControl;
+    mStreamControl = nullptr;
+    streamControl->CloseAll();
+    streamControl->Shutdown();
   }
 }