Make back button on stocks app search bar the accent color

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 '../painting/text_style.dart';
 import '../rendering/flex.dart';
 import '../theme/shadows.dart';
 import '../theme/typography.dart' as typography;
@@ skipping 12 matching lines @@
     this.backgroundColor
   }) : super(key: key);
 
   final Widget left;
   final Widget center;
   final List<Widget> right;
   final Color backgroundColor;
 
   Widget build() {
     Color toolbarColor = backgroundColor;
-    IconThemeColor iconThemeColor = IconThemeColor.white;
+    IconThemeData iconThemeData;
     TextStyle defaultTextStyle = typography.white.title;
     if (toolbarColor == null) {
       ThemeData themeData = Theme.of(this);
       toolbarColor = themeData.primaryColor;
       if (themeData.primaryColorBrightness == ThemeBrightness.light) {
-        iconThemeColor = IconThemeColor.black;
         defaultTextStyle = typography.black.title;
+        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: new DefaultTextStyle(
-              style: defaultTextStyle,
-              child: center
-            ),
+            child: center,
             padding: new EdgeDims.only(left: 24.0)
           )
         )
       );
     }
 
     if (right != null)
       children.addAll(right);
 
-    return new Container(
-      child: new IconTheme(
-        data: new IconThemeData(color: iconThemeColor),
+    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;
   }
 
 }