Source/WebCore/PAL/pal/PlatformAppleWin.cmake - WebKit - Git at Google

 list(APPEND PAL_FORWARDING_HEADERS_DIRECTORIES
     spi/cf
 )

 if (${USE_DIRECT2D})
 else ()
     list(APPEND PAL_FORWARDING_HEADERS_DIRECTORIES
         spi/cg
     )
 endif ()
	list(APPEND PAL_FORWARDING_HEADERS_DIRECTORIES
	spi/cf
	)

	if (${USE_DIRECT2D})
	else ()
	list(APPEND PAL_FORWARDING_HEADERS_DIRECTORIES
	spi/cg
	)
	endif ()