Reverted change to ServiceMap

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

Index: runtime/observatory/lib/src/service/object.dart
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index da3c349cdf62065949ce0b22d57a65c905b827ed..a519ed9d32df14f9642a4a23e1b844650f619a1d 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -1899,8 +1899,8 @@ class ObjectStore extends ServiceObject implements M.ObjectStore {
 }
 
 
-/// A [ServiceObject] which implements [ObservableMap].
-class ServiceMap extends ServiceObject implements M.UnknownObjectRef  {
+/// A [ServiceObject] which implements [Map].
+class ServiceMap extends ServiceObject implements Map, M.UnknownObjectRef  {
   final Map _map = {};
   static String objectIdRingPrefix = 'objects/';
 
@@ -4331,7 +4331,7 @@ bool _hasRef(String type) => type.startsWith('@');
 String _stripRef(String type) => (_hasRef(type) ? type.substring(1) : type);
 
 /// Recursively upgrades all [ServiceObject]s inside [collection] which must
-/// be an [ObservableMap] or an [ObservableList]. Upgraded elements will be
+/// be an [Map] or an [List]. Upgraded elements will be
 /// associated with [vm] and [isolate].
 void _upgradeCollection(collection, ServiceObjectOwner owner) {
   if (collection is ServiceMap) {