Start an AddressBook example (to test text fields)

sky/sdk/lib/widgets/tool_bar.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.
 
 import 'package:sky/widgets/theme.dart';
 
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/theme/shadows.dart';
 import 'package:sky/theme/typography.dart' as typography;
@@ skipping 29 matching lines @@
         iconThemeData = const IconThemeData(color: IconThemeColor.black);
       } else {
         iconThemeData = const IconThemeData(color: IconThemeColor.white);
       }
     }
 
     List<Widget> children = new List<Widget>();
     if (left != null)
       children.add(left);
 
-    if (center != null) {
-      children.add(
-        new Flexible(
-          child: new Padding(
-            child: center,
-            padding: new EdgeDims.only(left: 24.0)
-          )
+    children.add(
+      new Flexible(
+        child: new Padding(
+          child: center,
+          padding: new EdgeDims.only(left: 24.0)
         )
-      );
-    }
+      )
+    );
 
     if (right != null)
       children.addAll(right);
 
     Widget content = new Container(
       child: new DefaultTextStyle(
         style: defaultTextStyle,
         child: new Flex(
           [new Container(child: new Flex(children), height: kToolBarHeight)],
           alignItems: FlexAlignItems.end
         )
       ),
       padding: new EdgeDims.symmetric(horizontal: 8.0),
       decoration: new BoxDecoration(
         backgroundColor: toolbarColor,
         boxShadow: shadows[2]
       )
     );
 
     if (iconThemeData != null)
       content = new IconTheme(data: iconThemeData, child: content);
     return content;
   }
 
 }