Allow for embedder provided service request handlers

runtime/platform/json.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 PLATFORM_JSON_H_
 #define PLATFORM_JSON_H_
 
 #include "vm/allocation.h"
 #include "vm/globals.h"
 
@@ skipping 118 matching lines @@
   void AddUTF8(uint32_t ch);
   void AddEscapedChar(uint32_t ch);
   void AddString(const char* s);
   void AddEscapedString(const char* s);
 
   void Clear();
 
   char* buf() { return buf_; }
   intptr_t length() { return msg_len_; }
 
+  // Steal ownership of the buffer pointer.
+  // NOTE: TextBuffer is empty afterwards.
+  const char* Steal();
+
  private:
   void EnsureCapacity(intptr_t len);
   char* buf_;
   intptr_t buf_size_;
   intptr_t msg_len_;
 };
 
 }  // namespace dart
 
 #endif  // PLATFORM_JSON_H_