Add support for non ASCII strings when communicating with native ports

runtime/include/dart_api.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 INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
  *
  * Dart is a class-based programming language for creating structured
@@ skipping 895 matching lines @@
  */
 DART_EXPORT bool Dart_Post(Dart_Port port_id, Dart_Handle object);
 
 // --- Message sending/receiving from native code ----
 
 /**
  * A Dart_CObject is used for representing Dart objects as native C
  * data outside the Dart heap. These objects are totally detached from
  * the Dart heap. Only a subset of the Dart objects have a
  * representation as a Dart_CObject.
+ *
+ * The string encoding in the 'value.as_string' is UTF-8.
  */
 typedef struct _Dart_CObject {
   enum Type {
     kNull = 0,
     kBool,
     kInt32,
     kInt64,
     kBigint,
     kDouble,
     kString,
@@ skipping 1804 matching lines @@
  *
  * \param object An object.
  * \param peer A value to store in the peer field.
  *
  * \return Returns an error if 'object' is a subtype of Null, num, or
  *   bool.
  */
 DART_EXPORT Dart_Handle Dart_SetPeer(Dart_Handle object, void* peer);
 
 #endif  // INCLUDE_DART_API_H_