Reduce copying in sending service responses.

runtime/vm/json_stream.h

 // Copyright (c) 2013, 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 VM_JSON_STREAM_H_
 #define VM_JSON_STREAM_H_
 
 #include "include/dart_api.h"  // for Dart_Port
 #include "platform/text_buffer.h"
 #include "vm/allocation.h"
@@ skipping 79 matching lines @@
   void set_id_zone(ServiceIdZone* id_zone) {
     id_zone_ = id_zone;
   }
   ServiceIdZone* id_zone() {
     return id_zone_;
   }
 
   TextBuffer* buffer() { return &buffer_; }
   const char* ToCString() { return buffer_.buf(); }
 
-  void Steal(const char** buffer, intptr_t* buffer_length);
+  void Steal(char** buffer, intptr_t* buffer_length);
 
   void set_reply_port(Dart_Port port);
 
   void SetParams(const char** param_keys, const char** param_values,
                  intptr_t num_params);
 
   Dart_Port reply_port() const { return reply_port_; }
 
   intptr_t NumObjectParameters() const;
   RawObject* GetObjectParameterKey(intptr_t i) const;
@@ skipping 316 matching lines @@
 
   friend class JSONObject;
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(JSONArray);
 };
 
 }  // namespace dart
 
 #endif  // VM_JSON_STREAM_H_