Include 'fixedId' key when printing service ids

runtime/vm/json_test.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 "platform/assert.h"
 #include "platform/json.h"
 #include "vm/json_stream.h"
 #include "vm/unit_test.h"
 #include "vm/dart_api_impl.h"
 
@@ skipping 281 matching lines @@
 
 
 TEST_CASE(JSON_JSONStream_DartObject) {
   JSONStream js;
   {
     JSONArray jsarr(&js);
     jsarr.AddValue(Object::Handle(Object::null()));
     JSONObject jsobj(&jsarr);
     jsobj.AddProperty("object_key", Object::Handle(Object::null()));
   }
-  EXPECT_STREQ("[{\"type\":\"@null\",\"id\":\"objects\\/null\","
+  EXPECT_STREQ("[{\"type\":\"@null\",\"fixedId\":true,"
+               "\"id\":\"objects\\/null\","
                "\"valueAsString\":\"null\"},"
-               "{\"object_key\":{\"type\":\"@null\",\"id\":\"objects\\/null\","
+               "{\"object_key\":{\"type\":\"@null\",\"fixedId\":true,"
+               "\"id\":\"objects\\/null\","
                "\"valueAsString\":\"null\"}}]",
                js.ToCString());
 }
 
 TEST_CASE(JSON_JSONStream_EscapedString) {
   JSONStream js;
   {
     JSONArray jsarr(&js);
     jsarr.AddValue("Hel\"\"lo\r\n\t");
   }
@@ skipping 84 matching lines @@
   js.SetParams(&param_keys[0], &param_values[0], 2);
   EXPECT(js.num_params() == 2);
   EXPECT(!js.HasParam("lizard"));
   EXPECT(js.HasParam("dog"));
   EXPECT(js.HasParam("cat"));
   EXPECT(js.ParamIs("cat", "banana"));
   EXPECT(!js.ParamIs("dog", "banana"));
 }
 
 }  // namespace dart