Convert everything in the Sky API from degrees to radians.

Radians are the one true angle unit.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1164393002

examples/game/lib/transform_node.dart

@@ -123,7 +123,7 @@ class TransformNode {
     canvas.save();
     
     canvas.translate(_position[0], _position[1]);
-    canvas.rotateDegrees(_rotation);
+    canvas.rotate(degrees2radians(_rotation));
     canvas.translate(-_width*_pivot[0], -_height*_pivot[1]);
     
     // TODO: Use transformation matrix instead of individual calls

examples/raw/painting.sky

@@ -24,7 +24,7 @@ void main() {
 
     context.translate(mid.x, mid.y);
     paint.color = const Color.fromARGB(128, 255, 0, 255);
-    context.rotateDegrees(45.0);
+    context.rotate(math.PI/4.0);
 
     Gradient yellowBlue = new Gradient.Linear(
         [new Point(-radius, -radius), new Point(0.0, 0.0)],

examples/raw/sector_layout.dart

@@ -10,8 +10,6 @@ import 'package:sky/framework/rendering/object.dart';
 
 const double kTwoPi = 2 * math.PI;
 
-double deg(double radians) => radians * 180.0 / math.PI;
-
 class SectorConstraints {
   const SectorConstraints({
     this.minDeltaRadius: 0.0,
@@ -128,10 +126,10 @@ class RenderDecoratedSector extends RenderSector {
       Path path = new Path();
       double outerRadius = (parentData.radius + deltaRadius);
       Rect outerBounds = new Rect.fromLTRB(-outerRadius, -outerRadius, outerRadius, outerRadius);
-      path.arcTo(outerBounds, deg(parentData.theta), deg(deltaTheta), true);
+      path.arcTo(outerBounds, parentData.theta, deltaTheta, true);
       double innerRadius = parentData.radius;
       Rect innerBounds = new Rect.fromLTRB(-innerRadius, -innerRadius, innerRadius, innerRadius);
-      path.arcTo(innerBounds, deg(parentData.theta + deltaTheta), deg(-deltaTheta), false);
+      path.arcTo(innerBounds, parentData.theta + deltaTheta, -deltaTheta, false);
       path.close();
       canvas.drawPath(path, paint);
     }

examples/raw/spinning_image.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:math' as math;
 import 'dart:sky';
 import 'package:sky/framework/net/image_cache.dart' as image_cache;
 
@@ -16,7 +17,7 @@ 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.scale(0.2, 0.2);
   Paint paint = new Paint()..setARGB(255, 0, 255, 0);
   if (image != null)

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();

examples/spinning_arabic.dart

@@ -14,7 +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));