Remember when a variable has been expanded/unexpanded in the debugger.

runtime/observatory/lib/src/app/application.dart

Index: runtime/observatory/lib/src/app/application.dart
diff --git a/runtime/observatory/lib/src/app/application.dart b/runtime/observatory/lib/src/app/application.dart
index af467e2df8ae1d8f2d045b289e2e4c8617dba0e9..ff45043c2dad8080af056bc7a108495ba62744d3 100644
--- a/runtime/observatory/lib/src/app/application.dart
+++ b/runtime/observatory/lib/src/app/application.dart
@@ -226,4 +226,7 @@ class ObservatoryApplication extends Observable {
     Logger.root.warning('Caught exception: ${e}\n${st}');
     notifications.add(new Notification.fromException(e, st));
   }
+
+  // This map keeps track of which curly-blocks have been expanded by the user.
+  Map<String,bool> expansions = {};
 }