Define accelerated steps time function.

ui/gfx/geometry/cubic_bezier.h

-// Copyright 2014 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 UI_GFX_GEOMETRY_CUBIC_BEZIER_H_
-#define UI_GFX_GEOMETRY_CUBIC_BEZIER_H_
-
-#include "base/macros.h"
-#include "ui/gfx/gfx_export.h"
-
-namespace gfx {
-
-class GFX_EXPORT CubicBezier {
- public:
-  CubicBezier(double x1, double y1, double x2, double y2);
-  ~CubicBezier();
-
-  // Returns an approximation of y at the given x.
-  double Solve(double x) const;
-
-  // Returns an approximation of dy/dx at the given x.
-  double Slope(double x) const;
-
-  // Sets |min| and |max| to the bezier's minimum and maximium y values in the
-  // interval [0, 1].
-  void Range(double* min, double* max) const;
-
- private:
-  double x1_;
-  double y1_;
-  double x2_;
-  double y2_;
-
-  DISALLOW_ASSIGN(CubicBezier);
-};
-
-}  // namespace gfx
-
-#endif  // UI_GFX_GEOMETRY_CUBIC_BEZIER_H_