Remove Mac-specific includes from fx_system.h.

Change-Id: I4c9ca2c252d69cec8fdb53daf883e5ad73cccc48
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/70916
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxcrt/fx_system.h b/core/fxcrt/fx_system.h
index 1798c35..c0bd83f 100644
--- a/core/fxcrt/fx_system.h
+++ b/core/fxcrt/fx_system.h
@@ -43,11 +43,6 @@
 #include <sal.h>
 #endif  // defined(OS_WIN)
 
-#if defined(OS_MACOSX)
-#include <Carbon/Carbon.h>
-#include <libkern/OSAtomic.h>
-#endif  // defined(OS_MACOSX)
-
 #ifdef __cplusplus
 extern "C" {
 #endif  // __cplusplus