[Mac] Rely on science, not chance, to get the proper definition of the macro

Source/platform/geometry/FloatRect.h

Index: Source/platform/geometry/FloatRect.h
diff --git a/Source/platform/geometry/FloatRect.h b/Source/platform/geometry/FloatRect.h
index c7e2948096e3d49fea9c17ad94cffe1af9813768..661ca88a9ecfef63abfe8f6dcc9a1c5c4101891e 100644
--- a/Source/platform/geometry/FloatRect.h
+++ b/Source/platform/geometry/FloatRect.h
@@ -32,10 +32,9 @@
 
 #if OS(MACOSX)
 typedef struct CGRect CGRect;
-#ifdef NSGEOMETRY_TYPES_SAME_AS_CGGEOMETRY_TYPES
-typedef struct CGRect NSRect;
-#else
-typedef struct _NSRect NSRect;
+
+#ifdef __OBJC__
+#import <Foundation/Foundation.h>
 #endif
 #endif
 
@@ -167,7 +166,7 @@ public:
 #if OS(MACOSX)
     FloatRect(const CGRect&);
     operator CGRect() const;
-#if !defined(NSGEOMETRY_TYPES_SAME_AS_CGGEOMETRY_TYPES)
+#if defined(__OBJC__) && !defined(NSGEOMETRY_TYPES_SAME_AS_CGGEOMETRY_TYPES)
     FloatRect(const NSRect&);
     operator NSRect() const;
 #endif