Use an enum for Dart bindings for Skia Paint style

sky/engine/core/painting/Paint.cpp

Index: sky/engine/core/painting/Paint.cpp
diff --git a/sky/engine/core/painting/Paint.cpp b/sky/engine/core/painting/Paint.cpp
index a3f98099ac75f0678239c3b733aa136cb8f4d552..c11fa674d96c24e0b00b536af867af4103777dfa 100644
--- a/sky/engine/core/painting/Paint.cpp
+++ b/sky/engine/core/painting/Paint.cpp
@@ -37,6 +37,11 @@ void Paint::setMaskFilter(MaskFilter* filter)
     m_paint.setMaskFilter(filter->filter());
 }
 
+void Paint::setStyle(SkPaint::Style style)
+{
+    m_paint.setStyle(style);
+}
+
 void Paint::setTransferMode(SkXfermode::Mode transfer_mode)
 {
     m_paint.setXfermodeMode(transfer_mode);