Allow externalization of canonical strings also. Only restrict canonical strings

vm/dart_api_impl.cc

 // 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.
 
 #include "include/dart_api.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/dart.h"
@@ skipping 1769 matching lines @@
   if (array == NULL) {
     RETURN_NULL_ERROR(array);
   }
   intptr_t str_size = (str_obj.Length() * str_obj.CharSize());
   if ((length < str_size) || (length > String::kMaxElements)) {
     return Api::NewError("Dart_MakeExternalString "
                          "expects argument length to be in the range"
                          "[%"Pd"..%"Pd"].",
                          str_size, String::kMaxElements);
   }
-  if (str_obj.IsCanonical()) {
+  if (str_obj.InVMHeap()) {
     // Since the string object is read only we do not externalize
     // the string but instead copy the contents of the string into the
     // specified buffer and return a Null object.
     // This ensures that the embedder does not have to call again
     // to get at the contents.
     intptr_t copy_len = str_obj.Length();
     if (str_obj.IsOneByteString()) {
       ASSERT(length >= copy_len);
       uint8_t* latin1_array = reinterpret_cast<uint8_t*>(array);
       for (intptr_t i = 0; i < copy_len; i++) {
@@ skipping 2722 matching lines @@
   }
   {
     NoGCScope no_gc;
     RawObject* raw_obj = obj.raw();
     isolate->heap()->SetPeer(raw_obj, peer);
   }
   return Api::Success(isolate);
 }
 
 }  // namespace dart