Introduce Instance.kind.

runtime/observatory/tests/service/get_retained_size_rpc_test.dart

Index: runtime/observatory/tests/service/get_retained_size_rpc_test.dart
diff --git a/runtime/observatory/tests/service/get_retained_size_rpc_test.dart b/runtime/observatory/tests/service/get_retained_size_rpc_test.dart
index 9311ccf4af0aa0ceb5eb933c02d61bcadbd3021c..93740f3359ea1189c63e2b453e91c0a63ced96a2 100644
--- a/runtime/observatory/tests/service/get_retained_size_rpc_test.dart
+++ b/runtime/observatory/tests/service/get_retained_size_rpc_test.dart
@@ -35,7 +35,8 @@ var tests = [
       'targetId': evalResult['id'],
     };
     var result = await isolate.invokeRpcNoUpgrade('_getRetainedSize', params);
-    expect(result['type'], equals('@int'));
+    expect(result['type'], equals('@Instance'));
+    expect(result['kind'], equals('Int'));
     int value1 = int.parse(result['valueAsString']);
     expect(value1, isPositive);
 
@@ -46,7 +47,8 @@ var tests = [
       'targetId': evalResult['id'],
     };
     result = await isolate.invokeRpcNoUpgrade('_getRetainedSize', params);
-    expect(result['type'], equals('@int'));
+    expect(result['type'], equals('@Instance'));
+    expect(result['kind'], equals('Int'));
     int value2 = int.parse(result['valueAsString']);
     expect(value2, isPositive);
 
@@ -58,7 +60,8 @@ var tests = [
       'targetId': evalResult['class']['id'],
     };
     result = await isolate.invokeRpcNoUpgrade('_getRetainedSize', params);
-    expect(result['type'], equals('@int'));
+    expect(result['type'], equals('@Instance'));
+    expect(result['kind'], equals('Int'));
     int value3 = int.parse(result['valueAsString']);
     expect(value3, isPositive);
     expect(value3, equals(value2));