Adding _getBoolAttribute helper method

runtime/observatory/lib/src/elements/nav/menu_wrapper.dart

Index: runtime/observatory/lib/src/elements/nav/menu_wrapper.dart
diff --git a/runtime/observatory/lib/src/elements/nav/menu_wrapper.dart b/runtime/observatory/lib/src/elements/nav/menu_wrapper.dart
index b96fd0c935d45323466d59440e08104b007aa407..e0d32f9545dd01192b790c741df5c4f83582f367 100644
--- a/runtime/observatory/lib/src/elements/nav/menu_wrapper.dart
+++ b/runtime/observatory/lib/src/elements/nav/menu_wrapper.dart
@@ -37,7 +37,7 @@ class NavMenuElementWrapper extends HtmlElement {
     binder.registerCallback(this);
     _anchor = getAttribute('anchor');
     _link = getAttribute('link');
-    _last = getAttribute('') != null;
+    _last = _getBoolAttribute('last');
     createShadowRoot();
     render();
   }
@@ -58,4 +58,9 @@ class NavMenuElementWrapper extends HtmlElement {
         ..children = [new ContentElement()]
     ];
   }
+
+  bool _getBoolAttribute(String name) {
+    final String value = getAttribute(name);
+    return !(value == null || value == 'false');
+  }
 }