Small cleanup to Code and Profiler pages

runtime/bin/vmservice/client/lib/src/app/view_model.dart

Index: runtime/bin/vmservice/client/lib/src/app/view_model.dart
diff --git a/runtime/bin/vmservice/client/lib/src/app/view_model.dart b/runtime/bin/vmservice/client/lib/src/app/view_model.dart
index 993ff72af02b88f6b3730f5fa6e5e04b49a50264..0b90a993b6ce476d1cf305c2a60e4e2129c9e6b8 100644
--- a/runtime/bin/vmservice/client/lib/src/app/view_model.dart
+++ b/runtime/bin/vmservice/client/lib/src/app/view_model.dart
@@ -11,13 +11,21 @@ abstract class TableTreeRow extends Observable {
   @observable final List<String> columns = [];
   static const arrowRight = '\u2192';
   static const arrowDownRight = '\u21b3';
+  static const showExpanderStyle = 'cursor: pointer;';
+  static const hideExpanderStyle = 'visibility:hidden;';
+
   // TODO(johnmccutchan): Move expander display decisions into html once
   // tables and templates are better supported.
   @observable String expander = arrowRight;
+  @observable String expanderStyle = showExpanderStyle;
 
   TableTreeRow(TableTreeRow parent) :
       parent = parent,
-      depth = parent != null ? parent.depth+1 : 0;
+      depth = parent != null ? parent.depth+1 : 0 {
+    if (!hasChildren()) {
+      expanderStyle = hideExpanderStyle;
+    }
+  }
 
   bool _expanded = false;
   bool get expanded => _expanded;
@@ -41,6 +49,8 @@ abstract class TableTreeRow extends Observable {
     return expanded;
   }
 
+  bool hasChildren();
+
   /// Fired when the tree row is expanded. Add children rows here.
   void onShow();