Fixing SecurityKeySocket unit test issues and cleanup

remoting/host/security_key/security_key_socket.h

Index: remoting/host/security_key/security_key_socket.h
diff --git a/remoting/host/security_key/security_key_socket.h b/remoting/host/security_key/security_key_socket.h
index 069bd8119b36b3a53f278c8d94b1ba2eca8241aa..6b2576aa8e0dbbe24435ad3dc154694a5e9c4647 100644
--- a/remoting/host/security_key/security_key_socket.h
+++ b/remoting/host/security_key/security_key_socket.h
@@ -44,10 +44,11 @@ class SecurityKeySocket {
   bool GetAndClearRequestData(std::string* data_out);
 
   // Sends response data to the socket.
-  void SendResponse(const std::string& data);
+  void SendResponse(const std::string& data,
+                    const base::Closure& response_written_callback);
 
   // Sends an SSH error code to the socket.
-  void SendSshError();
+  void SendSshError(const base::Closure& error_sent_callback);
 
   // |request_received_callback| is used to notify the caller that request data
   // has been fully read, and caller is to use GetAndClearRequestData method to
@@ -91,6 +92,9 @@ class SecurityKeySocket {
   // Invoked when request data has been read.
   base::Closure request_received_callback_;
 
+  // Invoked when the response has been written.
+  base::Closure response_written_callback_;
+
   // Indicates whether read has completed and |request_received_callback_| is
   // about to be run.
   bool read_completed_;