Implement left property animation on InvalidatableStyleInterpolation

Source/core/animation/PrimitiveInterpolation.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 PrimitiveInterpolation_h
 #define PrimitiveInterpolation_h
 
 #include "core/animation/InterpolationValue.h"
+#include "platform/animation/AnimationUtilities.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Vector.h"
 #include <cmath>
 
 namespace blink {
 
 class StyleResolverState;
 
 // Represents a conversion from a pair of keyframes to something compatible with interpolation.
 // This is agnostic to whether the keyframes are compatible with each other or not.
 class PrimitiveInterpolation : public NoBaseWillBeGarbageCollectedFinalized<PrimitiveInterpolation> {
 public:
     virtual ~PrimitiveInterpolation() { }
 
-    virtual void interpolate(double fraction, OwnPtrWillBeMember<InterpolationValue>& result) const = 0;
+    virtual void interpolateValue(double fraction, OwnPtrWillBeMember<InterpolationValue>& result) const = 0;
+    virtual double interpolateUnderlyingFraction(double start, double end, double fraction) const = 0;
+    virtual bool isFlip() const { return false; }
 
     DEFINE_INLINE_VIRTUAL_TRACE() { }
 };
 
 // Represents a pair of keyframes that are compatible for "smooth" interpolation eg. "0px" and "100px".
 class PairwisePrimitiveInterpolation : public PrimitiveInterpolation {
 public:
     virtual ~PairwisePrimitiveInterpolation() { }
 
     static PassOwnPtrWillBeRawPtr<PairwisePrimitiveInterpolation> create(const InterpolationType& type, PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end, PassRefPtrWillBeRawPtr<NonInterpolableValue> nonInterpolableValue)
@@ skipping 15 matching lines @@
     }
 
 private:
     PairwisePrimitiveInterpolation(const InterpolationType& type, PassOwnPtrWillBeRawPtr<InterpolableValue> start, PassOwnPtrWillBeRawPtr<InterpolableValue> end, PassRefPtrWillBeRawPtr<NonInterpolableValue> nonInterpolableValue)
         : m_type(type)
         , m_start(start)
         , m_end(end)
         , m_nonInterpolableValue(nonInterpolableValue)
     { }
 
-    virtual void interpolate(double fraction, OwnPtrWillBeMember<InterpolationValue>& result) const override final
+    virtual void interpolateValue(double fraction, OwnPtrWillBeMember<InterpolationValue>& result) const override final
     {
         ASSERT(result);
         ASSERT(&result->type() == &m_type);
         ASSERT(result->nonInterpolableValue() == m_nonInterpolableValue.get());
         m_start->interpolate(*m_end, fraction, result->interpolableValue());
     }
 
+    virtual double interpolateUnderlyingFraction(double start, double end, double fraction) const override final { return blend(start, end, fraction); }
+
     const InterpolationType& m_type;
     OwnPtrWillBeMember<InterpolableValue> m_start;
     OwnPtrWillBeMember<InterpolableValue> m_end;
     RefPtrWillBeMember<NonInterpolableValue> m_nonInterpolableValue;
 };
 
 // Represents a pair of incompatible keyframes that fall back to 50% flip behaviour eg. "auto" and "0px".
 class FlipPrimitiveInterpolation : public PrimitiveInterpolation {
 public:
     virtual ~FlipPrimitiveInterpolation() { }
 
     static PassOwnPtrWillBeRawPtr<FlipPrimitiveInterpolation> create(PassOwnPtrWillBeRawPtr<InterpolationValue> start, PassOwnPtrWillBeRawPtr<InterpolationValue> end)
     {
         return adoptPtrWillBeNoop(new FlipPrimitiveInterpolation(start, end));
     }
 
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
         visitor->trace(m_start);
         visitor->trace(m_end);
         PrimitiveInterpolation::trace(visitor);
     }
 
 private:
     FlipPrimitiveInterpolation(PassOwnPtrWillBeRawPtr<InterpolationValue> start, PassOwnPtrWillBeRawPtr<InterpolationValue> end)
         : m_start(start)
         , m_end(end)
         , m_lastFraction(std::numeric_limits<double>::quiet_NaN())
-    {
-        ASSERT(m_start);
-        ASSERT(m_end);
-    }
+    { }
 
-    virtual void interpolate(double fraction, OwnPtrWillBeMember<InterpolationValue>& result) const override final
+    virtual void interpolateValue(double fraction, OwnPtrWillBeMember<InterpolationValue>& result) const override final
     {
         // TODO(alancutter): Remove this optimisation once Oilpan is default.
         if (!std::isnan(m_lastFraction) && (fraction < 0.5) == (m_lastFraction < 0.5))
             return;
-        result = ((fraction < 0.5) ? m_start : m_end)->clone();
+        const InterpolationValue* side = ((fraction < 0.5) ? m_start : m_end).get();
+        result = side ? side->clone() : nullptr;
         m_lastFraction = fraction;
     }
 
+    virtual double interpolateUnderlyingFraction(double start, double end, double fraction) const override final { return fraction < 0.5 ? start : end; }
+
+    virtual bool isFlip() const override final { return true; }
+
     OwnPtrWillBeMember<InterpolationValue> m_start;
     OwnPtrWillBeMember<InterpolationValue> m_end;
     mutable double m_lastFraction;
 };
 
 } // namespace blink
 
 #endif // PrimitiveInterpolation_h