Auto expand first profiler row when it has no siblings

runtime/bin/vmservice/client/lib/src/elements/isolate_profile.dart

 // Copyright (c) 2013, 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 isolate_profile_element;
 
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:logging/logging.dart';
 import 'package:observatory/service.dart';
@@ skipping 145 matching lines @@
     var root = profile.isolate.profileTrieRoot;
     if (root == null) {
       return;
     }
     try {
       tree.initialize(
           new ProfileCodeTrieNodeTreeRow(profile, root, root, null));
     } catch (e, stackTrace) {
       Logger.root.warning('_buildStackTree', e, stackTrace);
     }
+    // Check if we only have one node at the root and expand it.
+    if (tree.rows.length == 1) {
+      tree.toggle(0);
+    }
     notifyPropertyChange(#tree, null, tree);
   }
 
   void _buildTree() {
     _buildStackTree();
   }
 
   @observable String padding(TableTreeRow row) {
     return 'padding-left: ${row.depth * 16}px;';
   }
@@ skipping 18 matching lines @@
     if (row is TableRowElement) {
       // Subtract 1 to get 0 based indexing.
       try {
         tree.toggle(row.rowIndex - 1);
       }  catch (e, stackTrace) {
         Logger.root.warning('toggleExpanded', e, stackTrace);
       }
     }
   }
 }