Standardize on using "kind" to distinguish sub-varieties of a type.

runtime/vm/object_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/globals.h"
 
 #include "vm/assembler.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
@@ skipping 4510 matching lines @@
         "{\"type\":\"@null\",\"fixedId\":true,"
         "\"id\":\"objects\\/null\","
         "\"valueAsString\":\"null\"}",
         js.ToCString());
   }
   // Sentinel reference
   {
     JSONStream js;
     Object::sentinel().PrintJSON(&js, true);
     EXPECT_STREQ(
-        "{\"type\":\"Sentinel\",\"fixedId\":true,"
-        "\"id\":\"objects\\/not-initialized\","
+        "{\"type\":\"Sentinel\","
+        "\"kind\":\"NotInitialized\","
         "\"valueAsString\":\"<not initialized>\"}",
         js.ToCString());
   }
   // Transition sentinel reference
   {
     JSONStream js;
     Object::transition_sentinel().PrintJSON(&js, true);
     EXPECT_STREQ(
-        "{\"type\":\"Sentinel\",\"fixedId\":true,"
-        "\"id\":\"objects\\/being-initialized\","
+        "{\"type\":\"Sentinel\","
+        "\"kind\":\"BeingInitialized\","
         "\"valueAsString\":\"<being initialized>\"}",
         js.ToCString());
   }
   // LiteralToken reference.  This is meant to be an example of a
   // "weird" type that isn't usually returned by the VM Service except
   // when we are doing direct heap inspection.
   {
     JSONStream js;
     LiteralToken& tok = LiteralToken::Handle(LiteralToken::New());
     tok.PrintJSON(&js, true);
@@ skipping 117 matching lines @@
   // 2. Create an empty internalized LinkedHashMap in C++.
   Instance& dart_map = Instance::Handle();
   dart_map ^= Api::UnwrapHandle(h_result);
   LinkedHashMap& cc_map = LinkedHashMap::Handle(LinkedHashMap::NewDefault());
 
   // 3. Expect them to have identical structure.
   CheckIdenticalHashStructure(dart_map, cc_map);
 }
 
 }  // namespace dart