Define step timing function for the cc animation framework.

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/base/cc_export.h"
 #include "ui/gfx/geometry/cubic_bezier.h"
 
@@ skipping 63 matching lines @@
 };
 
 class CC_EXPORT EaseInOutTimingFunction {
  public:
   static scoped_ptr<TimingFunction> Create();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(EaseInOutTimingFunction);
 };
 
+class CC_EXPORT StepsTimingFunction : public TimingFunction {
+ public:
+  static scoped_ptr<StepsTimingFunction> Create(int steps,
+                                                float steps_start_offset);
+  ~StepsTimingFunction() override;
+
+  float GetValue(double t) const override;
+  scoped_ptr<TimingFunction> Clone() const override;
+
+  void Range(float* min, float* max) const override;
+  float Velocity(double time) const override;
+
+ protected:
+  StepsTimingFunction(int steps, float steps_start_offset);
+
+ private:
+  int steps_;
+  float steps_start_offset_;
+
+  DISALLOW_ASSIGN(StepsTimingFunction);
+};
+
 }  // namespace cc
 
 #endif  // CC_ANIMATION_TIMING_FUNCTION_H_