Modify AnimationEffect::sample() to return a CompositableValue

Source/core/animation/AnimationEffect.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 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef AnimationEffect_h
 #define AnimationEffect_h
 
-#include <wtf/PassRefPtr.h>
-#include <wtf/RefCounted.h>
+#include "CSSPropertyNames.h"
+#include "wtf/HashMap.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/RefCounted.h"
 
 namespace WebCore {
 
-class StylePropertySet;
+class AnimatableValue;
 
 class AnimationEffect : public RefCounted<AnimationEffect> {
+public:
+    // Encapsulates the value which results from applying a set of composition operations onto an
+    // underlying value. It is used to represent the output of the effect phase of the Web
+    // Animations model.
+    class CompositableValue : public RefCounted<CompositableValue> {
+    public:
+        virtual ~CompositableValue() { }
+        virtual AnimatableValue composite(const AnimatableValue&) const = 0;
+    };
 
-public:
-    static PassRefPtr<AnimationEffect> create();
-
-    PassRefPtr<StylePropertySet> sample(double fraction, int iteration);
-
-private:
-    AnimationEffect();
+    virtual ~AnimationEffect() { }
+    typedef HashMap<CSSPropertyID, RefPtr<CompositableValue> > CompositableValueMap;
+    virtual PassOwnPtr<CompositableValueMap> sample(int iteration, double fraction) const = 0;
 };
 
 } // namespace WebCore
 
 #endif // AnimationEffect_h