Add CHECK to make sure QuicHttpStream does not get destroyed during DoLoop

net/quic/quic_http_stream.h

Index: net/quic/quic_http_stream.h
diff --git a/net/quic/quic_http_stream.h b/net/quic/quic_http_stream.h
index 25eb3348844c6ffc83a2e6985ead31a357d2e6c0..e46ed0a09648e7e28817c924cb63f28580392dc0 100644
--- a/net/quic/quic_http_stream.h
+++ b/net/quic/quic_http_stream.h
@@ -207,6 +207,9 @@ class NET_EXPORT_PRIVATE QuicHttpStream
   // invoked.
   QuicClientPushPromiseIndex::TryHandle* push_handle_;
 
+  // Set to true when DoLoop() is being executed, false otherwise.
+  bool in_loop_;
+
   base::WeakPtrFactory<QuicHttpStream> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicHttpStream);