Baby steps towards an odeon-like animation system. First victim: Drawer.

sky/sdk/lib/base/lerp.dart

Index: sky/sdk/lib/base/lerp.dart
diff --git a/sky/sdk/lib/base/lerp.dart b/sky/sdk/lib/base/lerp.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c40934c024b8acf38d0343f66fa9cce123011326
--- /dev/null
+++ b/sky/sdk/lib/base/lerp.dart
@@ -0,0 +1,19 @@
+// 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';
+
+num lerpNum(num a, num b, double t) => a + (b - a) * t;
+
+Color lerpColor(Color a, Color b, double t) {
+  return new Color.fromARGB(
+      lerpNum(a.alpha, b.alpha, t).toInt(),
+      lerpNum(a.red, b.red, t).toInt(),
+      lerpNum(a.green, b.green, t).toInt(),
+      lerpNum(a.blue, b.blue, t).toInt());
+}
+
+Offset lerpOffset(Offset a, Offset b, double t) {
+  return new Offset(lerpNum(a.dx, b.dx, t), lerpNum(a.dy, b.dy, t));
+}