Store [-webkit-]transform-origin as a TransformOrigin.

Source/core/rendering/style/TransformOrigin.h

+// Copyright 2014 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 TransformOrigin_h
+#define TransformOrigin_h
+
+#include "platform/Length.h"
+
+namespace blink {
+
+class TransformOrigin {
+public:
+    TransformOrigin() { }

[Timothy Loh, 2014/10/10 15:04:48]

Is this ctor ever used?

+    TransformOrigin(const Length& x, const Length& y, float z) : m_x(x), m_y(y), m_z(z) { }
+    bool operator==(const TransformOrigin& o) const { return m_x == o.m_x && m_y == o.m_y && m_z == o.m_z; }
+    bool operator!=(const TransformOrigin& o) const { return !(*this == o); }
+    const Length& x() const { return m_x; }
+    const Length& y() const { return m_y; }
+    float z() const { return m_z; }
+private:
+    Length m_x;
+    Length m_y;
+    float m_z;
+};
+
+} // namespace blink
+
+#endif // TransformOrigin_h