Bug 1231213 - IPCStreamSource should not attempt to read from its stream if already closed. r=asuth

Differential Revision: https://phabricator.services.mozilla.com/D26161

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

ipc/glue/IPCStreamSource.cpp

@@ -243,6 +243,13 @@ void IPCStreamSource::OnStreamReady(Callback* aCallback) {
   MOZ_ASSERT(aCallback == mCallback);
   mCallback->ClearSource();
   mCallback = nullptr;
+
+  // Possibly closed if this callback is (indirectly) called by
+  // IPCStreamSourceParent::RecvRequestClose().
+  if (mState == eClosed) {
+    return;
+  }
+
   DoRead();
 }