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:
+  enum StepAtPosition { Start, Middle, End };

[ajuma, 2014/12/17 16:32:56]

This doesn't seem to be used anywhere. Were you planning on using it instead of
steps_start_offset? (It seems nicer to use the enum if these are the only
offsets we need to support.) 

If the enum is going to be used, let's make this an enum class since these are
now allowed (see
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/Q5WmkAImanc).

[loyso (OOO), 2014/12/18 01:53:05]

I forgot to erase this enum. I had the initial implementation (not presented
here) using enums. See my comment below.

+
+  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_