Add VR Shell animation classes and unit test.

chrome/browser/android/vr_shell/easing.cc

+// Copyright 2016 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.
+
+#include "chrome/browser/android/vr_shell/easing.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+
+namespace vr_shell {
+namespace easing {
+
+double Easing::CalculateValue(double input) {
+  DCHECK(input >= 0.0 && input <= 1.0);
+  return CalculateValueImpl(input);
+}
+
+CubicBezier::CubicBezier(double p1x, double p1y, double p2x, double p2y)
+    : bezier_(p1x, p1y, p2x, p2y) {}
+
+double CubicBezier::CalculateValueImpl(double state) {
+  return bezier_.Solve(state);
+}
+
+EaseIn::EaseIn(double power) : power_(power) {}
+double EaseIn::CalculateValueImpl(double state) {
+  return pow(state, power_);
+}
+
+EaseOut::EaseOut(double power) : power_(power) {}
+double EaseOut::CalculateValueImpl(double state) {
+  return 1.0 - pow(1.0 - state, power_);
+}
+
+double Linear::CalculateValueImpl(double state) {
+  return state;
+}
+
+}  // namespace easing
+}  // namespace vr_shell