Avoid sending double responding close control frames in WebSockets

net/websockets/websocket_channel.cc

Index: net/websockets/websocket_channel.cc
diff --git a/net/websockets/websocket_channel.cc b/net/websockets/websocket_channel.cc
index da32e2eea85446747666233f77a77fbedec9d0d8..8310aece7d5fe503ae0c27bd70ebf1380ad1a725 100644
--- a/net/websockets/websocket_channel.cc
+++ b/net/websockets/websocket_channel.cc
@@ -477,7 +477,8 @@ ChannelState WebSocketChannel::SendFlowControl(int64_t quota) {
 
     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();