Bug 1581067 - P3 - Suppress the error reuslt for open stream; r=asuth

Differential Revision: https://phabricator.services.mozilla.com/D47451

--HG--
extra : moz-landing-system : lando

dom/cache/Manager.cpp

@@ -1452,7 +1452,15 @@ class Manager::OpenStreamAction final : public Manager::BaseAction {
   }
 
   virtual void Complete(Listener* aListener, ErrorResult&& aRv) override {
-    mResolver(std::move(mBodyStream));
+    if (aRv.Failed()) {
+      // Ignore the reason for fail and just pass a null input stream to let it
+      // fail.
+      aRv.SuppressException();
+      mResolver(nullptr);
+    } else {
+      mResolver(std::move(mBodyStream));
+    }
+
     mResolver = nullptr;
   }