Cleanup of SkyBinding, and resultant yak shaving.

sky/examples/rendering/spinning_flex.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:sky' as sky;
 import 'dart:math' as math;
 
-import 'package:sky/app/scheduler.dart';
+import 'package:sky/base/scheduler.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/rendering/sky_binding.dart';
 import 'package:vector_math/vector_math.dart';
 
 import '../lib/solid_color_box.dart';
 
 double timeBase;
 RenderTransform transformBox;
 
@@ skipping 22 matching lines @@
 void rotate(double timeStamp) {
   if (timeBase == null)
     timeBase = timeStamp;
   double delta = (timeStamp - timeBase) / 1000; // radians
 
   transformBox.setIdentity();
   transformBox.translate(transformBox.size.width / 2.0, transformBox.size.height / 2.0);
   transformBox.rotateZ(delta);
   transformBox.translate(-transformBox.size.width / 2.0, -transformBox.size.height / 2.0);
 }