Make back button on stocks app search bar the accent color

sky/sdk/lib/widgets/icon_button.dart

Index: sky/sdk/lib/widgets/icon_button.dart
diff --git a/sky/sdk/lib/widgets/icon_button.dart b/sky/sdk/lib/widgets/icon_button.dart
index 2b39ec2579ba5520710d694052ab318738eb88bd..dbcd0af46b3dde4a9c513815cf60e35a8b8d9a6d 100644
--- a/sky/sdk/lib/widgets/icon_button.dart
+++ b/sky/sdk/lib/widgets/icon_button.dart
@@ -2,6 +2,8 @@
 // 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';
@@ -9,16 +11,25 @@ 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)