Implemented additive animations for length

Source/core/animation/Interpolation.h

Index: Source/core/animation/Interpolation.h
diff --git a/Source/core/animation/Interpolation.h b/Source/core/animation/Interpolation.h
index 88f49f15d8fdf6b89d2c699e65d713f8a9c3e446..58c00d6f0d2252223fcad34e86edea912db7fea8 100644
--- a/Source/core/animation/Interpolation.h
+++ b/Source/core/animation/Interpolation.h
@@ -5,6 +5,7 @@
 #ifndef Interpolation_h
 #define Interpolation_h
 
+#include "core/animation/AnimationEffect.h"
 #include "core/animation/InterpolableValue.h"
 #include "platform/heap/Handle.h"
 
@@ -19,8 +20,19 @@ public:
 
     virtual ~Interpolation();
 
+    static PassRefPtrWillBeRawPtr<Interpolation> create(PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end,
+        AnimationEffect::CompositeOperation compositeStart, AnimationEffect::CompositeOperation compositeEnd)
+    {
+        return adoptRefWillBeNoop(new Interpolation(start, end, compositeStart, compositeEnd));
+    }
+
     void interpolate(int iteration, double fraction) const;
 
+    const InterpolableValue& cachedValue() const { return *m_cachedValue.get(); }
+    double cachedUnderlyingFraction() const { return m_cachedUnderlyingFraction; }
+
+    bool isReplaceOnly() const { return m_compositeStart == AnimationEffect::CompositeReplace && m_compositeEnd == AnimationEffect::CompositeReplace; }

[alancutter (OOO until 2018), 2015/02/12 05:55:45]

We want to just check for UF == 0. Let's not have this function as the name may
be confusing and just check UF directly.

+
     virtual bool isStyleInterpolation() const { return false; }
     virtual bool isLegacyStyleInterpolation() const { return false; }
 
@@ -29,12 +41,18 @@ public:
 protected:
     const OwnPtrWillBeMember<InterpolableValue> m_start;
     const OwnPtrWillBeMember<InterpolableValue> m_end;
+    const AnimationEffect::CompositeOperation m_compositeStart;
+    const AnimationEffect::CompositeOperation m_compositeEnd;
 
     mutable double m_cachedFraction;
     mutable int m_cachedIteration;
     mutable OwnPtrWillBeMember<InterpolableValue> m_cachedValue;
+    mutable double m_cachedUnderlyingFraction;
 
+    // FIXME: Remove old constructor?
     Interpolation(PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end);
+    Interpolation(PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end,
+        AnimationEffect::CompositeOperation compositeStart, AnimationEffect::CompositeOperation compositeEnd);
 
 private:
     InterpolableValue* getCachedValueForTesting() const { return m_cachedValue.get(); }