Define step timing function for the cc animation framework.

public/platform/WebTransformAnimationCurve.h

 /*
  * Copyright (C) 2012 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:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 24 matching lines @@
 class WebTransformAnimationCurve : public WebCompositorAnimationCurve {
 public:
     virtual ~WebTransformAnimationCurve() { }
 
     // Adds the keyframe with the default timing function (ease).
     virtual void add(const WebTransformKeyframe&) = 0;
     virtual void add(const WebTransformKeyframe&, TimingFunctionType) = 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 WebTransformKeyframe&, double x1, double y1, double x2, double y2) = 0;
+    // Adds the keyframe with a steps timing function.
+    virtual void add(const WebTransformKeyframe&, int steps, float stepsStartOffset) = 0;
 };
 
 } // namespace blink
 
 #endif // WebTransformAnimationCurve_h