Misc Observatory tweaks.

runtime/observatory/lib/src/elements/class_tree.dart

Index: runtime/observatory/lib/src/elements/class_tree.dart
diff --git a/runtime/observatory/lib/src/elements/class_tree.dart b/runtime/observatory/lib/src/elements/class_tree.dart
index d9d2814be42d6ac825fb5d1917e4c60e4fb1f530..879431d835768a1f2800999baa1c9754d1cbddeb 100644
--- a/runtime/observatory/lib/src/elements/class_tree.dart
+++ b/runtime/observatory/lib/src/elements/class_tree.dart
@@ -94,7 +94,8 @@ class ClassTreeElement extends HtmlElement implements Renderable {
       new DivElement()
         ..classes = ['content-centered']
         ..children = [
-          new HeadingElement.h1()..text = 'Class Hierarchy',
+          new HeadingElement.h1()
+            ..text = 'Class Hierarchy (${_subclasses.length})',
           new BRElement(),
           new HRElement(),
           _object == null