Implement left property animation on InvalidatableStyleInterpolation

Source/core/animation/LengthInterpolationType.h

Index: Source/core/animation/LengthInterpolationType.h
diff --git a/Source/core/animation/LengthInterpolationType.h b/Source/core/animation/LengthInterpolationType.h
new file mode 100644
index 0000000000000000000000000000000000000000..bf70157810d9ee7d9d60f4b96e74806f61457342
--- /dev/null
+++ b/Source/core/animation/LengthInterpolationType.h
@@ -0,0 +1,28 @@
+// 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 LengthInterpolationType_h
+#define LengthInterpolationType_h
+
+#include "core/animation/InterpolationType.h"
+#include "core/animation/LengthPropertyFunctions.h"
+
+namespace blink {
+
+class LengthInterpolationType : public InterpolationType {
+public:
+    LengthInterpolationType(CSSPropertyID);
+
+    virtual PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertSingle(const CSSPropertySpecificKeyframe&, const StyleResolverState*, ConversionCheckers&) const final;
+    virtual PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertUnderlyingValue(const StyleResolverState&) const override final;
+    virtual void apply(const InterpolableValue&, const NonInterpolableValue*, StyleResolverState&) const override final;
+
+private:
+    const ValueRange m_valueRange;
+    const LengthPropertyFunctions::LengthSetter m_lengthSetter;
+};
+
+} // namespace blink
+
+#endif // LengthInterpolationType_h