Support per property CSS Animation stacks

Source/core/animation/InvalidatableStyleInterpolation.h

 // Copyright 2015 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 InvalidatableStyleInterpolation_h
 #define InvalidatableStyleInterpolation_h
 
 #include "core/animation/InterpolationType.h"
 #include "core/animation/InterpolationValue.h"
 #include "core/animation/PrimitiveInterpolation.h"
 #include "core/animation/StyleInterpolation.h"
 
 namespace blink {
 
 // TODO(alancutter): This class will replace *StyleInterpolation, SVGInterpolation, Interpolation.
 // For now it needs to distinguish itself during the refactor and temporarily has an ugly name.
 // TODO(alancutter): Make this class generic for any animation environment so it can be reused for SVG animations.
 class CORE_EXPORT InvalidatableStyleInterpolation : public StyleInterpolation {
 public:
     static PassRefPtr<InvalidatableStyleInterpolation> create(
         const Vector<const InterpolationType*>& InterpolationTypes,
         const CSSPropertySpecificKeyframe& startKeyframe,
         const CSSPropertySpecificKeyframe& endKeyframe)
     {
         return adoptRef(new InvalidatableStyleInterpolation(InterpolationTypes, startKeyframe, endKeyframe));
     }
 
     virtual void interpolate(int iteration, double fraction);
-    virtual void apply(StyleResolverState&) const;
+    bool dependsOnUnderlyingValue() const;
+    virtual void apply(StyleResolverState&) const { ASSERT_NOT_REACHED(); }
+    static void applyStack(const ActiveInterpolations&, StyleResolverState&);
 
     virtual bool isInvalidatableStyleInterpolation() const { return true; }
 
 private:
     InvalidatableStyleInterpolation(
         const Vector<const InterpolationType*>& InterpolationTypes,
         const CSSPropertySpecificKeyframe& startKeyframe,
         const CSSPropertySpecificKeyframe& endKeyframe);
 
     PassOwnPtr<InterpolationValue> maybeConvertUnderlyingValue(const StyleResolverState&) const;
-    void ensureValidInterpolation(const StyleResolverState&, const InterpolationValue* underlyingValue) const;
-    bool dependsOnUnderlyingValue() const;
+    const InterpolationValue* ensureValidInterpolation(const StyleResolverState&, const InterpolationValue* underlyingValue) const;
     bool isCacheValid(const StyleResolverState&, const InterpolationValue* underlyingValue) const;
     bool isNeutralKeyframeActive() const;
     bool maybeCachePairwiseConversion(const StyleResolverState*, const InterpolationValue* underlyingValue) const;
     PassOwnPtr<InterpolationValue> convertSingleKeyframe(const CSSPropertySpecificKeyframe&, const StyleResolverState&, const InterpolationValue* underlyingValue) const;
     void setFlagIfInheritUsed(StyleResolverState&) const;
 
     const Vector<const InterpolationType*>& m_interpolationTypes;
     const CSSPropertySpecificKeyframe* m_startKeyframe;
     const CSSPropertySpecificKeyframe* m_endKeyframe;
     double m_currentFraction;
     mutable OwnPtr<PrimitiveInterpolation> m_cachedConversion;
     mutable InterpolationType::ConversionCheckers m_conversionCheckers;
     mutable OwnPtr<InterpolationValue> m_cachedValue;
 };
 
 DEFINE_TYPE_CASTS(InvalidatableStyleInterpolation, Interpolation, value, value->isInvalidatableStyleInterpolation(), value.isInvalidatableStyleInterpolation());
 
 } // namespace blink
 
 #endif // InvalidatableStyleInterpolation_h