Add RPC and UI for reachable size of an object / all instances of a class.

runtime/observatory/tests/service/test_helper.dart

 // 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.
 
 library test_helper;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'package:observatory/service_io.dart';
@@ skipping 301 matching lines @@
   for (var i = 0; i < rootLib.classes.length; i++) {
     Class cls = rootLib.classes[i];
     if (cls.name == className) {
       return cls;
     }
   }
   return null;
 }
 
 
+Future<Instance> rootLibraryFieldValue(Isolate isolate,
+                                       String fieldName) async {
+  Library rootLib = await isolate.rootLibrary.load();
+  Field field = rootLib.variables.singleWhere((v) => v.name == fieldName);
+  await field.load();
+  Instance value = field.staticValue;
+  await value.load();
+  return value;
+}
+
+
 /// Runs [tests] in sequence, each of which should take an [Isolate] and
 /// return a [Future]. Code for setting up state can run before and/or
 /// concurrently with the tests. Uses [mainArgs] to determine whether
 /// to run tests or testee in this invokation of the script.
 Future runVMTests(List<String> mainArgs,
                   List<VMTest> tests,
                   {Future testeeBefore(),
                    Future testeeConcurrent(),
                    bool pause_on_start: false,
                    bool pause_on_exit: false,
@@ skipping 37 matching lines @@
       }, onError: (e, st) {
         process.requestExit();
         if (!_isWebSocketDisconnect(e)) {
           print('Unexpected exception in service tests: $e $st');
           throw e;
         }
       });
     });
   }
 }