Support additive animations on CSS property transform

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

+// 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 LengthUnitsChecker_h
+#define LengthUnitsChecker_h
+
+#include "core/animation/InterpolationType.h"
+#include "core/css/CSSPrimitiveValue.h"
+#include "core/css/resolver/StyleResolverState.h"
+
+namespace blink {
+
+class LengthUnitsChecker : public InterpolationType::ConversionChecker {
+public:
+    static PassOwnPtr<LengthUnitsChecker> maybeCreate(CSSLengthArray&& lengthArray, const StyleResolverState& state)
+    {
+        bool create = false;
+        size_t lastIndex = 0;
+        for (size_t i = 0; i < lengthArray.values.size(); i++) {
+            if (i == CSSPrimitiveValue::UnitTypePercentage || !lengthArray.typeFlags.get(i))
+                continue;
+            lengthArray.values[i] = lengthUnit(i, state.cssToLengthConversionData());
+            create = true;
+            lastIndex = i;
+        }
+        if (!create)
+            return nullptr;
+        return adoptPtr(new LengthUnitsChecker(std::move(lengthArray), lastIndex));
+    }
+
+    bool isValid(const InterpolationEnvironment& environment, const InterpolationValue& underlying) const final
+    {
+        for (size_t i = 0; i <= m_lastIndex; i++) {
+            if (i == CSSPrimitiveValue::UnitTypePercentage || !m_lengthArray.typeFlags.get(i))
+                continue;
+            if (m_lengthArray.values[i] != lengthUnit(i, environment.state().cssToLengthConversionData()))
+                return false;
+        }
+        return true;
+    }
+
+    static double lengthUnit(size_t lengthUnitType, const CSSToLengthConversionData& conversionData)
+    {
+        return conversionData.zoomedComputedPixels(1, CSSPrimitiveValue::lengthUnitTypeToUnitType(static_cast<CSSPrimitiveValue::LengthUnitType>(lengthUnitType)));
+    }
+
+private:
+    LengthUnitsChecker(CSSPrimitiveValue::CSSLengthArray&& lengthArray, size_t lastIndex)
+        : m_lengthArray(std::move(lengthArray))
+        , m_lastIndex(lastIndex)
+    { }
+
+    const CSSLengthArray m_lengthArray;
+    const size_t m_lastIndex;
+};
+
+} // namespace blink
+
+#endif // LengthUnitsChecker_h