Convert everything in the Sky API from degrees to radians.

sky/examples/raw/spinning_square.dart

Index: sky/examples/raw/spinning_square.dart
diff --git a/sky/examples/raw/spinning_square.dart b/sky/examples/raw/spinning_square.dart
index dbc0140d08711e0c1e2ac5daa27a75280633f9e5..97c3c7ab413ace874edd4986b93b1c595672f71d 100644
--- a/sky/examples/raw/spinning_square.dart
+++ b/sky/examples/raw/spinning_square.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:sky';
+import 'dart:math' as math;
 
 double timeBase = null;
 
@@ -13,7 +14,7 @@ void beginFrame(double timeStamp) {
   double delta = timeStamp - timeBase;
   PictureRecorder canvas = new PictureRecorder(view.width, view.height);
   canvas.translate(view.width / 2.0, view.height / 2.0);
-  canvas.rotateDegrees(delta / 10);
+  canvas.rotate(math.PI * delta / 1800);
   canvas.drawRect(new Rect.fromLTRB(-100.0, -100.0, 100.0, 100.0),
                   new Paint()..setARGB(255, 0, 255, 0));
   view.picture = canvas.endRecording();