Implement CSSOM Smooth Scroll API

public/platform/WebAnimation.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 29 matching lines @@
 namespace blink {
 
 class WebAnimationCurve;
 
 // A compositor driven animation.
 class WebAnimation {
 public:
     enum TargetProperty {
         TargetPropertyTransform = 0,
         TargetPropertyOpacity,
-        TargetPropertyFilter
+        TargetPropertyFilter,
+        TargetPropertyScrollOffset
     };
 
     virtual ~WebAnimation() { }
 
     // An id is effectively the animation's name, and it is not unique.
     virtual int id() = 0;
 
     virtual TargetProperty targetProperty() const = 0;
 
     // This is the number of times that the animation will play. If this
     // value is zero the animation will not play. If it is negative, then
     // the animation will loop indefinitely.
     virtual int iterations() const = 0;
     virtual void setIterations(int) = 0;
 
     virtual double startTime() const = 0;
     virtual void setStartTime(double monotonicTime) = 0;
 
     virtual double timeOffset() const = 0;
     virtual void setTimeOffset(double monotonicTime) = 0;
 
     // If alternatesDirection is true, on odd numbered iterations we reverse the curve.
     virtual bool alternatesDirection() const = 0;
     virtual void setAlternatesDirection(bool) = 0;
 };
 
 } // namespace blink
 
 #endif // WebAnimation_h