WIP: Implement CSS transitions on top of InterpolationTypes instead of AnimatableValues

third_party/WebKit/Source/core/animation/PairwiseInterpolation.h

Index: third_party/WebKit/Source/core/animation/PairwiseInterpolation.h
diff --git a/third_party/WebKit/Source/core/animation/PairwiseInterpolation.h b/third_party/WebKit/Source/core/animation/PairwiseInterpolation.h
new file mode 100644
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+++ b/third_party/WebKit/Source/core/animation/PairwiseInterpolation.h
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+// Copyright 2016 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 PairwiseInterpolation_h
+#define PairwiseInterpolation_h
+
+#include "core/animation/PrimitiveInterpolation.h"
+#include "core/animation/StackableInterpolation.h"
+#include "core/animation/TypedInterpolationValue.h"
+
+namespace blink {
+
+class PairwiseInterpolation : public StackableInterpolation {
+public:
+    static PassRefPtr<PairwiseInterpolation> maybeCreate(const InterpolationType& type, InterpolationValue&& start, InterpolationValue&& end)
+    {
+        PairwiseInterpolationValue merge = type.maybeMergeSingles(start.clone(), end.clone());
+        if (!merge)
+            return nullptr;
+        return adoptRef(new PairwiseInterpolation(type, std::move(start), std::move(end), std::move(merge)));
+    }
+
+    bool isPairwiseInterpolation() const final { return true; }
+
+    PropertyHandle getProperty() const final
+    {
+        return m_property;
+    }
+
+protected:
+    PairwiseInterpolation(const InterpolationType& type, InterpolationValue&& start, InterpolationValue&& end, PairwiseInterpolationValue&& merge)
+        : m_property(type.getProperty())
+        , m_start(TypedInterpolationValue::create(type, std::move(start)))
+        , m_end(TypedInterpolationValue::create(type, std::move(end)))
+        , m_pairwisePrimitiveInterpolation(PairwisePrimitiveInterpolation::create(type, std::move(merge)))
+        , m_currentValue(m_pairwisePrimitiveInterpolation->initialValue())
+    { }
+
+    void interpolateImpl() final
+    {
+        if (m_currentFraction == 0)
+            m_currentValue->mutableValue() = m_start->value().clone();
+        else if (m_currentFraction == 1)
+            m_currentValue->mutableValue() = m_end->value().clone();
+        else
+            m_pairwisePrimitiveInterpolation->interpolateValue(m_currentFraction, m_currentValue);
+    }
+
+    std::unique_ptr<TypedInterpolationValue> maybeConvertUnderlyingValue(const InterpolationEnvironment&) const final
+    {
+        NOTREACHED();
+        return nullptr;
+    }
+
+    const TypedInterpolationValue* ensureValidInterpolation(const InterpolationEnvironment&, const UnderlyingValueOwner&) const final
+    {
+        return m_currentValue.get();
+    }
+
+    double underlyingFraction() const final
+    {
+        return 0;
+    }
+
+    const PropertyHandle m_property;
+    const std::unique_ptr<TypedInterpolationValue> m_start;
+    const std::unique_ptr<TypedInterpolationValue> m_end;
+    const std::unique_ptr<PairwisePrimitiveInterpolation> m_pairwisePrimitiveInterpolation;
+    std::unique_ptr<TypedInterpolationValue> m_currentValue;
+};
+
+} // namespace blink
+
+#endif // PairwiseInterpolation_h