Make back button on stocks app search bar the accent color

sky/sdk/example/stocks/lib/stock_home.dart

Index: sky/sdk/example/stocks/lib/stock_home.dart
diff --git a/sky/sdk/example/stocks/lib/stock_home.dart b/sky/sdk/example/stocks/lib/stock_home.dart
index 0868fd1f68e7947b457f2ea55067aa3c2a53cc84..e57aeda63ed645258d89b547319126a882e801ba 100644
--- a/sky/sdk/example/stocks/lib/stock_home.dart
+++ b/sky/sdk/example/stocks/lib/stock_home.dart
@@ -252,11 +252,14 @@ class StockHome extends AnimatedComponent {
     return new ToolBar(
       left: new IconButton(
         icon: "navigation/arrow_back",
-        onPressed: _handleSearchEnd),
+        color: Theme.of(this).accentColor,
+        onPressed: _handleSearchEnd
+      ),
       center: new Input(
         focused: true,
         placeholder: 'Search stocks',
-        onChanged: _handleSearchQueryChanged),
+        onChanged: _handleSearchQueryChanged
+      ),
       backgroundColor: Theme.of(this).canvasColor
     );
   }