Avoid sending double responding close control frames in WebSockets

net/websockets/websocket_channel.cc

 // Copyright 2013 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.
 
 #include "net/websockets/websocket_channel.h"
 
 #include <limits.h>  // for INT_MAX
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 459 matching lines @@
       return CHANNEL_DELETED;
     if (bytes_to_send < data_size) {
       front.DidConsume(bytes_to_send);
       front.ResetOpcode();
       return CHANNEL_ALIVE;
     }
     quota -= bytes_to_send;
 
     pending_received_frames_.pop();
   }
-  if (pending_received_frames_.empty() && has_received_close_frame_) {
+  if (!InClosingState() && pending_received_frames_.empty() &&
+      has_received_close_frame_) {
     // We've been waiting for the client to consume the frames before
     // responding to the closing handshake initiated by the server.
     return RespondToClosingHandshake();
   }
 
   // If current_receive_quota_ == 0 then there is no pending ReadFrames()
   // operation.
   const bool start_read =
       current_receive_quota_ == 0 && quota > 0 &&
       (state_ == CONNECTED || state_ == SEND_CLOSED || state_ == CLOSE_WAIT);
@@ skipping 705 matching lines @@
 }
 
 void WebSocketChannel::CloseTimeout() {
   stream_->Close();
   SetState(CLOSED);
   DoDropChannel(false, kWebSocketErrorAbnormalClosure, "");
   // |this| has been deleted.
 }
 
 }  // namespace net