Update arrow in stocks search to use ColorFilter

We changed IconButton to require a ColorFilter to filter the color of the icon.

examples/raw/painting.dart

@@ -83,7 +83,7 @@ ui.Picture paint(ui.Rect paintBounds) {
 ui.Scene composite(ui.Picture picture, ui.Rect paintBounds) {
   final double devicePixelRatio = ui.view.devicePixelRatio;
   ui.Rect sceneBounds = new ui.Rect.fromLTWH(0.0, 0.0, ui.view.width * devicePixelRatio, ui.view.height * devicePixelRatio);
-  Float32List deviceTransform = new Float32List(16)
+  Float64List deviceTransform = new Float64List(16)
     ..[0] = devicePixelRatio
     ..[5] = devicePixelRatio
     ..[10] = 1.0

examples/stocks/lib/stock_home.dart

@@ -224,7 +224,7 @@ class StockHomeState extends State<StockHome> {
     return new ToolBar(
       left: new IconButton(
         icon: "navigation/arrow_back",
-        color: Theme.of(context).accentColor,
+        colorFilter: new ui.ColorFilter.mode(Theme.of(context).accentColor, ui.TransferMode.srcATop),
         onPressed: _handleSearchEnd
       ),
       center: new Input(