Change how we provide value previews in the vm service.

runtime/vm/service.cc

 // 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.
 
 #include "vm/service.h"
 
 #include "include/dart_api.h"
 #include "platform/globals.h"
 
 #include "vm/compiler.h"
@@ skipping 1100 matching lines @@
   return true;
 }
 
 
 static void PrintPseudoNull(JSONStream* js,
                             const char* id,
                             const char* preview) {
   JSONObject jsobj(js);
   jsobj.AddProperty("type", "Null");
   jsobj.AddProperty("id", id);
-  jsobj.AddProperty("preview", preview);
+  jsobj.AddProperty("valueAsString", preview);
 }
 
 
 static RawObject* LookupObjectId(Isolate* isolate,
                                  const char* arg,
                                  bool* error) {
   *error = false;
   if (strncmp(arg, "int-", 4) == 0) {
     arg += 4;
     int64_t value = 0;
@@ skipping 754 matching lines @@
   while (current != NULL) {
     if (strcmp(name, current->name()) == 0) {
       return current;
     }
     current = current->next();
   }
   return NULL;
 }
 
 }  // namespace dart