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

Source/core/rendering/style/StyleTransformData.h

Index: Source/core/rendering/style/StyleTransformData.h
diff --git a/Source/core/rendering/style/StyleTransformData.h b/Source/core/rendering/style/StyleTransformData.h
index 34ed026f5e3ff0268f77d457fb885d53bbcff072..58c823e50686683379988acda9694eacfa3b5fab 100644
--- a/Source/core/rendering/style/StyleTransformData.h
+++ b/Source/core/rendering/style/StyleTransformData.h
@@ -25,7 +25,7 @@
 #ifndef StyleTransformData_h
 #define StyleTransformData_h
 
-#include "platform/Length.h"
+#include "core/rendering/style/TransformOrigin.h"
 #include "platform/transforms/TransformOperations.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ -44,9 +44,7 @@ public:
     }
 
     TransformOperations m_operations;
-    Length m_x;
-    Length m_y;
-    float m_z;
+    TransformOrigin m_origin;
 
 private:
     StyleTransformData();