Use typedefs from header

Reviewed By: gkassabli

Differential Revision: D4036421

fbshipit-source-id: 01f15cb840363850970e6a60e661af06fd6ec9e0

React/CSSLayout/CSSLayout.c

@@ -91,12 +91,8 @@ typedef struct CSSNode {
 
   struct CSSNode *nextChild;
 
-  CSSSize (*measure)(void *context,
-                     float width,
-                     CSSMeasureMode widthMode,
-                     float height,
-                     CSSMeasureMode heightMode);
-  void (*print)(void *context);
+  CSSMeasureFunc measure;
+  CSSPrintFunc print;
   void *context;
 } CSSNode;