Introduce CSSNodeCopyStyle

Summary:
- Add a convenience function to copy all style from one node to another.
- CSSNodeIsDirty will return true after this function if any style was changed in the destination node.

Reviewed By: emilsjolander

Differential Revision: D4188514

fbshipit-source-id: af8d7fb5e8688c64aea05ce7ad23fff9233fb441

CSSLayout/CSSLayout.h

@@ -98,6 +98,8 @@ WIN_EXPORT bool CSSNodeCanUseCachedMeasurement(const CSSMeasureMode widthMode,
                                                const float marginRow,
                                                const float marginColumn);
 
+WIN_EXPORT void CSSNodeCopyStyle(const CSSNodeRef dstNode, const CSSNodeRef srcNode);
+
 #define CSS_NODE_PROPERTY(type, name, paramName)                           \
   WIN_EXPORT void CSSNodeSet##name(const CSSNodeRef node, type paramName); \
   WIN_EXPORT type CSSNodeGet##name(const CSSNodeRef node);