Define step timing function for the cc animation framework.

public/platform/WebFilterAnimationCurve.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 29 matching lines @@
 
 // A keyframed filter animation curve.
 class WebFilterAnimationCurve : public WebCompositorAnimationCurve {
 public:
     virtual ~WebFilterAnimationCurve() { }
 
     virtual void add(const WebFilterKeyframe&, TimingFunctionType = TimingFunctionTypeEase) = 0;
     // Adds the keyframe with a custom, bezier timing function. Note, it is
     // assumed that x0 = y0 = 0, and x3 = y3 = 1.
     virtual void add(const WebFilterKeyframe&, double x1, double y1, double x2, double y2) = 0;
+    // Adds the keyframe with a steps timing function.
+    virtual void add(const WebFilterKeyframe&, int steps, float stepsStartOffset) = 0;
 };
 
 } // namespace blink
 
 #endif // WebFilterAnimationCurve_h