fixes #52, fields shadowing getters/setters or other fields

test/codegen/expect/sunflower/sunflower.js

Index: test/codegen/expect/sunflower/sunflower.js
diff --git a/test/codegen/expect/sunflower/sunflower.js b/test/codegen/expect/sunflower/sunflower.js
index ec7f75ccde32fc1c5167476ed1fef91e27ae5798..afb8dc8e9f73fd9c508d37da0b2fb3d006f6f9fe 100644
--- a/test/codegen/expect/sunflower/sunflower.js
+++ b/test/codegen/expect/sunflower/sunflower.js
@@ -47,14 +47,14 @@ var sunflower;
   }
   class Circle extends core.Object {
     Circle(x, y, radius) {
-      this.x = x;
-      this.y = y;
-      this.radius = radius;
+      dart.initField(Circle, this, 'x', x);
+      dart.initField(Circle, this, 'y', y);
+      dart.initField(Circle, this, 'radius', radius);
     }
   }
   class CirclePainter extends core.Object {
     CirclePainter() {
-      this.color = ORANGE;
+      dart.initField(CirclePainter, this, 'color', ORANGE);
     }
     draw() {
       exports.context.beginPath();