[vm] Remove Dart_MakeExternalString and --support-externalizable-strings

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 RUNTIME_INCLUDE_DART_API_H_
 #define RUNTIME_INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
@@ skipping 1816 matching lines @@
  *
  * \param str A String.
  * \param length Returns the storage size in bytes of the String.
  *  This is the size in bytes needed to store the String.
  *
  * \return A valid handle if no error occurs during the operation.
  */
 DART_EXPORT Dart_Handle Dart_StringStorageSize(Dart_Handle str, intptr_t* size);
 
 /**
- * Converts a String into an ExternalString.
- * The original object is morphed into an external string object.
- *
- * \param array External space into which the string data will be
- *   copied into. This must not move.
- * \param external_allocation_size The size in bytes of the provided external
- *   space (array). Used to inform the garbage collector.
- * \param peer An external pointer to associate with this string.
- * \param cback A callback to be called when this string is finalized.
- *
- * \return the converted ExternalString object if no error occurs.
- *   Otherwise returns an error handle.
- *   If the object is a valid string but if it cannot be externalized
- *   the string data is copied into the external space specified
- *   and the passed in peer is setup as a peer for this string object.
- *   In this case the function returns the original String object as is.
- *
- * For example:
- *  intptr_t size;
- *  Dart_Handle result;
- *  result = DartStringStorageSize(str, &size);
- *  void* data = malloc(size);
- *  result = Dart_MakeExternalString(str, data, size, NULL, NULL);
- *
- */
-DART_EXPORT Dart_Handle
-Dart_MakeExternalString(Dart_Handle str,
-                        void* array,
-                        intptr_t external_allocation_size,
-                        void* peer,
-                        Dart_PeerFinalizer cback);
-
-/**
  * Retrieves some properties associated with a String.
  * Properties retrieved are:
  * - character size of the string (one or two byte)
  * - length of the string
  * - peer pointer of string if it is an external string.
  * \param str A String.
  * \param char_size Returns the character size of the String.
  * \param str_len Returns the length of the String.
  * \param peer Returns the peer pointer associated with the String or 0 if
  *   there is no peer pointer for it.
@@ skipping 1472 matching lines @@
  *  compiled with DART_PRECOMPILED_RUNTIME).
  */
 DART_EXPORT bool Dart_IsPrecompiledRuntime();
 
 /**
  *  Print a native stack trace. Used for crash handling.
  */
 DART_EXPORT void Dart_DumpNativeStackTrace(void* context);
 
 #endif /* INCLUDE_DART_API_H_ */ /* NOLINT */