Make stocksapp.dart almost pass the dart analyzer.

sky/framework/fn.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 library fn;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:sky' as sky;
 import 'reflect.dart' as reflect;
 
 bool _initIsInCheckedMode() {
-  void testFn(double i) {}
+  String testFn(i) { double d = i; return d.toString(); }
   try {
     testFn('not a double');
   } catch (ex) {
     return true;
   }
   return false;
 }
 
 final bool _isInCheckedMode = _initIsInCheckedMode();
 final bool _shouldLogRenderDuration = false;
@@ skipping 374 matching lines @@
     oldElement._children = null;
     return false;
   }
 }
 
 class Container extends Element {
 
   String get _tagName => 'div';
 
   static final Container _emptyContainer = new Container();
-
   Element get _emptyElement => _emptyContainer;
 
   Container({
     Object key,
     List<Node> children,
     Style style,
     String inlineStyle
   }) : super(
     key: key,
     children: children,
@@ skipping 44 matching lines @@
       skyImage.style['height'] = '${height}px';
     }
   }
 }
 
 class Anchor extends Element {
 
   String get _tagName => 'a';
 
   static final Anchor _emptyAnchor = new Anchor();
+  Element get _emptyElement => _emptyAnchor;
 
   String href;
+  int width;
+  int height;
 
   Anchor({
     Object key,
     List<Node> children,
     Style style,
     String inlineStyle,
     this.width,
     this.height,
     this.href
   }) : super(
@@ skipping 166 matching lines @@
 
       _sync(null, _host, null);
       assert(_root is sky.Node);
 
       sw.stop();
       if (_shouldLogRenderDuration)
         print("Initial render: ${sw.elapsedMicroseconds} microseconds");
     });
   }
 }