Add a complex reload test that rebases the root script path three times.

runtime/observatory/lib/src/service/object.dart

 // Copyright (c) 2014, 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.
 
 part of service;
 
 // Some value smaller than the object ring, so requesting a large array
 // doesn't result in an expired ref because the elements lapped it in the
 // object ring.
 const int kDefaultFieldLimit = 100;
@@ skipping 1315 matching lines @@
     }
     if (startPos != null) {
       params['tokenPos'] = startPos;
     }
     if (endPos != null) {
       params['endTokenPos'] = endPos;
     }
     return invokeRpc('getSourceReport', params);
   }
 
-  Future<ServiceMap> reloadSources() {
-    return invokeRpc('_reloadSources', {}).then((_) {
+  Future<ServiceMap> reloadSources(
+      [Map<String, dynamic> params]) {

[turnidge, 2016/11/18 19:23:10]

I would prefer a named optional parameter for "rootLibUri".

[Cutch, 2016/11/18 20:23:19]

Done.

+    if (params == null) {
+      params = <String, dynamic>{};
+    }
+    return invokeRpc('reloadSources', params).then((result) {
       reloading = true;
+      return result;
     });
   }
 
   void _handleIsolateReloadEvent(ServiceEvent event) {
     reloading = false;
     if (event.reloadError != null) {
       // Failure.
       print('Reload failed: ${event.reloadError}');
     } else {
       _cache.clear();
@@ skipping 3048 matching lines @@
     var v = list[i];
     if ((v is Map) && _isServiceMap(v)) {
       list[i] = owner.getFromMap(v);
     } else if (v is List) {
       _upgradeList(v, owner);
     } else if (v is Map) {
       _upgradeMap(v, owner);
     }
   }
 }