Define accelerated steps time function.

cc/animation/timing_function.h

Index: cc/animation/timing_function.h
diff --git a/cc/animation/timing_function.h b/cc/animation/timing_function.h
index 056ad41419357eb4e6771801296d3f7b920c6e4e..18186f42e266eaa218ae0ed5cc495164cd65a086 100644
--- a/cc/animation/timing_function.h
+++ b/cc/animation/timing_function.h
@@ -54,6 +54,25 @@ class CC_EXPORT CubicBezierTimingFunction : public TimingFunction {
   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();