Animation: Allow CC per-curve timing functions to be steps timing functions

public/platform/WebFloatAnimationCurve.h

Index: public/platform/WebFloatAnimationCurve.h
diff --git a/public/platform/WebFloatAnimationCurve.h b/public/platform/WebFloatAnimationCurve.h
index 15397deaac16fbf341f120f36adbef45dd94156f..74d9e8d278ae8e4a171388b3aa1b7ccd90f7f82e 100644
--- a/public/platform/WebFloatAnimationCurve.h
+++ b/public/platform/WebFloatAnimationCurve.h
@@ -46,6 +46,11 @@ public:
     // Adds the keyframe with a steps timing function.
     virtual void add(const WebFloatKeyframe&, int steps, float stepsStartOffset) = 0;
 
+    virtual void setLinearTimingFunction() = 0;
+    virtual void setCubicBezierTimingFunction(TimingFunctionType) = 0;
+    virtual void setCubicBezierTimingFunction(double x1, double y1, double x2, double y2) = 0;
+    virtual void setStepsTimingFunction(int numberOfSteps, float stepsStartOffset) = 0;
+
     virtual float getValue(double time) const = 0;
 };