Improve isolate list. Expose isolate origin.

runtime/observatory/tests/service/get_isolate_rpc_test.dart

 // Copyright (c) 2015, 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.
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 
 import 'test_helper.dart';
 
 var tests = [
   (VM vm) async {
     var params = {
       'isolateId': vm.isolates.first.id,
     };
     var result = await vm.invokeRpcNoUpgrade('getIsolate', params);
     expect(result['type'], equals('Isolate'));
     expect(result['id'], startsWith('isolates/'));
     expect(result['number'], new isInstanceOf<String>());
+    expect(result['_originNumber'], equals(result['number']));
     expect(result['startTime'], isPositive);
     expect(result['livePorts'], isPositive);
     expect(result['pauseOnExit'], isFalse);
     expect(result['pauseEvent']['type'], equals('Event'));
     expect(result['error'], isNull);
     expect(result['rootLib']['type'], equals('@Library'));
     expect(result['libraries'].length, isPositive);
     expect(result['libraries'][0]['type'], equals('@Library'));
     expect(result['breakpoints'].length, isZero);
     expect(result['_heaps']['new']['type'], equals('HeapSpace'));
@@ skipping 23 matching lines @@
       'isolateId': 'isolates/9999999999',
     };
     var result = await vm.invokeRpcNoUpgrade('getIsolate', params);
     expect(result['type'], equals('Sentinel'));
     expect(result['kind'], equals('Collected'));
     expect(result['valueAsString'], equals('<collected>'));
   },
 ];
 
 main(args) async => runVMTests(args, tests);