Define accelerated steps time function.

cc/animation/timing_function.h

 // Copyright 2012 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 CC_ANIMATION_TIMING_FUNCTION_H_
 #define CC_ANIMATION_TIMING_FUNCTION_H_
 
 #include "cc/animation/animation_curve.h"
 #include "cc/base/cc_export.h"
 #include "third_party/skia/include/core/SkScalar.h"
@@ skipping 36 matching lines @@
 
   double x1_;
   double y1_;
   double x2_;
   double y2_;
 
  private:
   DISALLOW_ASSIGN(CubicBezierTimingFunction);
 };
 
+class CC_EXPORT StepsTimingFunction : public TimingFunction {
+ public:
+  static scoped_ptr<StepsTimingFunction> Create(int steps, bool stepsAtStart);

[ajuma, 2014/02/21 19:05:08]

nit: steps_at_start

+  virtual ~StepsTimingFunction();
+
+  virtual float GetValue(double time) const OVERRIDE;
+  virtual scoped_ptr<AnimationCurve> Clone() const OVERRIDE;
+  virtual void Range(float* min, float* max) const OVERRIDE;
+
+ protected:
+  StepsTimingFunction(int steps, bool stepsAtStart);

[ajuma, 2014/02/21 19:05:08]

nit: steps_at_start

+
+  int steps_;
+  bool stepsAtStart_;

[ajuma, 2014/02/21 19:05:08]

nit: steps_at_start_

+
+ private:
+  DISALLOW_ASSIGN(StepsTimingFunction);
+};
+
 class CC_EXPORT EaseTimingFunction {
  public:
   static scoped_ptr<TimingFunction> Create();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(EaseTimingFunction);
 };
 
 class CC_EXPORT EaseInTimingFunction {
  public:
@@ skipping 15 matching lines @@
  public:
   static scoped_ptr<TimingFunction> Create();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(EaseInOutTimingFunction);
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_TIMING_FUNCTION_H_