Do not crash on null stream in writing to bidirectional streams

net/http/bidirectional_stream.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_HTTP_BIDIRECTIONAL_STREAM_H_
 #define NET_HTTP_BIDIRECTIONAL_STREAM_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 63 matching lines @@
     // The delegate should not call BidirectionalStream::Cancel
     // during this callback.
     virtual void OnDataSent() = 0;
 
     // Called when trailers are received. This is called as soon as trailers
     // are received, which can happen before a read completes.
     // The delegate is able to continue reading if there is no pending read and
     // EOF has not been received, or to send data if there is no pending send.
     virtual void OnTrailersReceived(const SpdyHeaderBlock& trailers) = 0;
 
-    // Called when the stream is closed or an error occurred.
-    // No other delegate functions will be called after this.
+    // Called when an error occurred. Do not call into the stream after this
+    // point.

[kapishnikov, 2016/06/01 22:09:49]

I think it is important to keep the contract that no other delegate functions
can be called after OnFailed(), at least these calls should not be propagated to
the bidirectional stream client.

[xunjieli, 2016/06/01 23:08:22]

Done.

     virtual void OnFailed(int error) = 0;
 
    protected:
     virtual ~Delegate();
 
    private:
     DISALLOW_COPY_AND_ASSIGN(Delegate);
   };
 
   // Constructs a BidirectionalStream. |request_info| contains information about
@@ skipping 148 matching lines @@
   std::vector<scoped_refptr<IOBuffer>> write_buffer_list_;
   // List of buffer length.
   std::vector<int> write_buffer_len_list_;
 
   DISALLOW_COPY_AND_ASSIGN(BidirectionalStream);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_BIDIRECTIONAL_STREAM_H_