Eliminate need for va_copy in json.cc

runtime/bin/dbg_connection.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef BIN_DBG_CONNECTION_H_
 #define BIN_DBG_CONNECTION_H_
 
 #include "bin/builtin.h"
 #include "bin/utils.h"
 
@@ skipping 32 matching lines @@
   static void CloseDbgConnection();
 
   static void HandleMessages();
   static void HandleResumeCmd(const char* msg);
   static void HandleStepIntoCmd(const char* msg);
   static void HandleStepOverCmd(const char* msg);
   static void HandleStepOutCmd(const char* msg);
   static void HandleGetLibraryURLsCmd(const char* json_msg);
   static void HandleGetScriptURLsCmd(const char* json_msg);
 
-  static void SendError(int msg_id, const char* format, ...);
+  static void SendError(int msg_id, const char* err_msg);
 
   static bool handler_started_;
 
   static bool request_resume_;
 
   // The socket that is listening for incoming debugger connections.
   // This descriptor is created and closed by a VM thread.
   static int listener_fd_;
 
   // The socket that connects with the debugger client.
   // The descriptor is created by the debugger connection thread and
   // closed by a VM thread.
   static int debugger_fd_;
 
   // The VM thread waits on this condition variable when it reaches a
   // breakpoint and the debugger client has not connected yet.
   static dart::Monitor is_connected_;
 
   static MessageBuffer* msgbuf_;
 
   friend class DebuggerConnectionImpl;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(DebuggerConnectionHandler);
 };
 
 #endif  // BIN_DBG_CONNECTION_H_