Make back button on stocks app search bar the accent color

sky/sdk/lib/widgets/icon_button.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 'dart:sky' as sky;
+
 import '../rendering/box.dart';
 import 'basic.dart';
 import 'icon.dart';
 import 'widget.dart';
 
 class IconButton extends Component {
 
-  IconButton({ String icon: '', this.onPressed })
+  IconButton({ String icon: '', this.onPressed, this.color })
     : super(key: icon), icon = icon;
 
   final String icon;
   final Function onPressed;
+  final Color color;
 
   Widget build() {
+    Widget child = new Icon(type: icon, size: 24);
+    if (color != null) {
+      child = new ColorFilter(
+        color: color,
+        transferMode: sky.TransferMode.srcATop,
+        child: child
+      );
+    }
     return new Listener(
       child: new Padding(
-        child: new Icon(type: icon, size: 24),
+        child: child,
         padding: const EdgeDims.all(8.0)),
       onGestureTap: (_) {
         if (onPressed != null)
           onPressed();
       }
     );
   }
 
 }