Implement left property animation on InvalidatableStyleInterpolation

Source/core/animation/LengthPropertyFunctions.h

Index: Source/core/animation/LengthPropertyFunctions.h
diff --git a/Source/core/animation/LengthPropertyFunctions.h b/Source/core/animation/LengthPropertyFunctions.h
new file mode 100644
index 0000000000000000000000000000000000000000..311ad5e79f5e19df839c09f0e552a313006f9aeb
--- /dev/null
+++ b/Source/core/animation/LengthPropertyFunctions.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 LengthPropertyFunctions_h
+#define LengthPropertyFunctions_h
+
+#include "core/CSSPropertyNames.h"
+#include "core/CSSValueKeywords.h"
+#include "platform/Length.h"
+
+namespace blink {
+
+class ComputedStyle;
+
+class LengthPropertyFunctions {
+public:
+    typedef void (ComputedStyle::*LengthSetter)(const Length&);
+
+    static ValueRange valueRange(CSSPropertyID);
+    static bool getPixelsForKeyword(CSSPropertyID, CSSValueID, double& resultPixels);
+    static bool getLength(CSSPropertyID, const ComputedStyle&, Length& result);
+    static bool getInitialLength(CSSPropertyID, Length& result);
+};
+
+} // namespace blink
+
+#endif // LengthPropertyFunctions_h