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

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

--HG--
branch : FIREFOX_ESR_68_6_X_RELBRANCH
extra : source : 63afe468c6a580c6c01623fd60c8393fc2c2a4e0

dom/cache/StreamList.cpp

@@ -133,7 +133,15 @@ void StreamList::Close(const nsID& aId) {
 void StreamList::CloseAll() {
   NS_ASSERT_OWNINGTHREAD(StreamList);
   if (mStreamControl) {
-    mStreamControl->CloseAll();
+    auto streamControl = mStreamControl;
+    mStreamControl = nullptr;
+
+    streamControl->CloseAll();
+
+    mStreamControl = streamControl;
+    streamControl = nullptr;
+
+    mStreamControl->Shutdown();
   }
 }