privatize and remove some fields in Isolate response

runtime/observatory/tests/service/get_isolate_rpc_test.dart

Index: runtime/observatory/tests/service/get_isolate_rpc_test.dart
diff --git a/runtime/observatory/tests/service/get_isolate_rpc_test.dart b/runtime/observatory/tests/service/get_isolate_rpc_test.dart
index 146ff5f7053533c401627f2d80f7f8de181c50f2..6414ae2a0bc0a4e17ca298bc788f81b19c2e804b 100644
--- a/runtime/observatory/tests/service/get_isolate_rpc_test.dart
+++ b/runtime/observatory/tests/service/get_isolate_rpc_test.dart
@@ -26,10 +26,8 @@ var tests = [
     expect(result['libraries'].length, isPositive);
     expect(result['libraries'][0]['type'], equals('@Library'));
     expect(result['breakpoints'].length, isZero);
-    expect(result['features'].length, isPositive);
-    expect(result['features'][0], new isInstanceOf<String>());
-    expect(result['heaps']['new']['type'], equals('HeapSpace'));
-    expect(result['heaps']['old']['type'], equals('HeapSpace'));
+    expect(result['_heaps']['new']['type'], equals('HeapSpace'));
+    expect(result['_heaps']['old']['type'], equals('HeapSpace'));
   },
 ];