Do not crash on null stream in writing to bidirectional streams

net/spdy/bidirectional_stream_spdy_impl.h

 // Copyright 2015 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_SPDY_BIDIRECTIONAL_STREAM_SPDY_IMPL_H_
 #define NET_SPDY_BIDIRECTIONAL_STREAM_SPDY_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 52 matching lines @@
   SpdyResponseHeadersStatus OnResponseHeadersUpdated(
       const SpdyHeaderBlock& response_headers) override;
   void OnDataReceived(std::unique_ptr<SpdyBuffer> buffer) override;
   void OnDataSent() override;
   void OnTrailers(const SpdyHeaderBlock& trailers) override;
   void OnClose(int status) override;
 
  private:
   int SendRequestHeadersHelper();
   void OnStreamInitialized(int rv);
+  // Notifies delegate of an error.
+  void NotifyError(int rv);
   void ScheduleBufferedRead();
   void DoBufferedRead();
   bool ShouldWaitForMoreBufferedData() const;
 
   const base::WeakPtr<SpdySession> spdy_session_;
   const BidirectionalStreamRequestInfo* request_info_;
   BidirectionalStreamImpl::Delegate* delegate_;
   std::unique_ptr<base::Timer> timer_;
   SpdyStreamRequest stream_request_;
   base::WeakPtr<SpdyStream> stream_;
@@ skipping 23 matching lines @@
   scoped_refptr<IOBuffer> pending_combined_buffer_;
 
   base::WeakPtrFactory<BidirectionalStreamSpdyImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BidirectionalStreamSpdyImpl);
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_BIDIRECTIONAL_STREAM_SPDY_IMPL_H_