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

runtime/observatory/lib/src/elements/debugger.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.
 
 library debugger_page_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:observatory/cli.dart';
@@ skipping 1699 matching lines @@
       busy = false;
     });
   }
 
   @observable String scriptHeight;
   @observable bool expanded = false;
   @observable bool busy = false;
 
   DebuggerFrameElement.created() : super.created();
 
+
+  String makeExpandKey(String key) {
+    return '${frame.function.qualifiedName}/${key}';
+  }
+
   bool matchFrame(Frame newFrame) {
     return newFrame.function.id == frame.function.id;
   }
 
   void updateFrame(Frame newFrame) {
     assert(matchFrame(newFrame));
     frame = newFrame;
   }
 
   Script get script => frame.location.script;
@@ skipping 271 matching lines @@
         }
       });
   }
 
   void focus() {
     $['textBox'].focus();
   }
 
   DebuggerInputElement.created() : super.created();
 }