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

net/quic/quic_http_stream.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_QUIC_QUIC_HTTP_STREAM_H_
 #define NET_QUIC_QUIC_HTTP_STREAM_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 189 matching lines @@
   // True when this stream receives a go away from server due to port migration.
   bool port_migration_detected_;
 
   bool found_promise_;
   // |QuicClientPromisedInfo| owns this. It will be set when |Try()|
   // is asynchronous, i.e. it returned QUIC_PENDING, and remains valid
   // until |OnRendezvouResult()| fires or |push_handle_->Cancel()| is
   // 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);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_HTTP_STREAM_H_