Add VR Shell animation classes and unit test.

chrome/browser/android/vr_shell/easing.h

+// 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.
+
+#ifndef CHROME_BROWSER_ANDROID_VR_SHELL_EASING_H_
+#define CHROME_BROWSER_ANDROID_VR_SHELL_EASING_H_
+
+#include "ui/gfx/geometry/cubic_bezier.h"
+
+namespace vr_shell {
+
+enum EasingType {

[David Trainor- moved to gerrit, 2016/09/14 21:43:29]

Any reason to keep these outside the easing namespace?

Also do these types warrant a comment?

[cjgrant, 2016/09/16 17:47:08]

Done.  Also, I removed the EasingType, as Easing itself doesn't need this (will
add it later when needed).

+  LINEAR = 0,
+  CUBICBEZIER,
+  EASEIN,
+  EASEOUT
+};
+
+class Easing {

[David Trainor- moved to gerrit, 2016/09/14 21:43:30]

Should this just be called Interpolator?  At least that's what the the Android
version is called.

[cjgrant, 2016/09/16 17:47:08]

It could be, but as per
http://www.w3schools.com/cssref/css3_pr_transition-timing-function.asp, "easing"
seems appropriate too (and maybe better, as it isn't Android specific).  If you
feel strongly about this, I'll certainly change it.  :)

[David Trainor- moved to gerrit, 2016/09/16 21:25:44]

Not particularly :).  Just a suggestion.

+ public:
+  virtual double CalculateValue(double state) = 0;

[David Trainor- moved to gerrit, 2016/09/14 21:43:30]

Should we add a comment specifying the expected input range?  0 - 1?

[cjgrant, 2016/09/16 17:47:08]

Done.

+  virtual ~Easing() {}
+ protected:

[David Trainor- moved to gerrit, 2016/09/14 21:43:30]

new line before protected and private

Same for all other classes?

[cjgrant, 2016/09/16 17:47:08]

Done.

[cjgrant, 2016/09/16 17:47:08]

Done.

+  Easing() {}
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Easing);
+};
+
+namespace easing {
+
+class CubicBezier : public Easing {
+ public:
+  CubicBezier(double p1x, double p1y, double p2x, double p2y);
+  double CalculateValue(double state) override;
+ private:

[David Trainor- moved to gerrit, 2016/09/14 21:43:30]

I forget if you still need DISALLOW_COPY_AND_ASSIGN on the subclasses, but I
think generally it's added?

[cjgrant, 2016/09/16 17:47:08]

Done.

+  gfx::CubicBezier bezier_;
+};
+
+class EaseIn : public Easing {
+ public:
+  explicit EaseIn(double power);
+  double CalculateValue(double state) override;
+ private:
+  double power_;
+};
+
+class EaseOut : public Easing {
+ public:
+  explicit EaseOut(double power);
+  double CalculateValue(double state) override;
+ private:
+  double power_;
+};
+
+class Linear : public Easing {
+ public:
+  double CalculateValue(double state) override;
+};
+
+}  // namespace easing
+
+}  // namespace vr_shell
+
+#endif  // CHROME_BROWSER_ANDROID_VR_SHELL_EASING_H_