Handle direction control in compositor Animations

public/platform/WebCompositorAnimation.h

 // Copyright 2014 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 WebCompositorAnimation_h
 #define WebCompositorAnimation_h
 
 #define WEB_ANIMATION_SUPPORTS_FRACTIONAL_ITERATIONS 1
+#define WEB_ANIMATION_SUPPORTS_FULL_DIRECTION 1
 
 namespace blink {
 
 // A compositor driven animation.
 class WebCompositorAnimation {
 public:
     enum TargetProperty {
         TargetPropertyTransform = 0,
         TargetPropertyOpacity,
         TargetPropertyFilter,
         TargetPropertyScrollOffset
     };
 
+    enum Direction {
+        DirectionNormal = 0,
+        DirectionReverse,
+        DirectionAlternate,
+        DirectionAlternateReverse
+    };
+
     virtual ~WebCompositorAnimation() { }
 
     // 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 double iterations() const = 0;
     virtual void setIterations(double) = 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;
+    virtual Direction direction() const = 0;
+    virtual void setDirection(Direction) = 0;
 };
 
 } // namespace blink
 
 #endif // WebCompositorAnimation_h