gm: Include system_preferences.h in mac file.

This fixes the FIXME in there.

R=epoger@google.com

Review URL: https://codereview.appspot.com/6576049

git-svn-id: http://skia.googlecode.com/svn/trunk@5692 2bbb7eff-a529-9590-31e7-b0007b416f81

gm/system_preferences_mac.mm

@@ -5,10 +5,9 @@
  * found in the LICENSE file.
  */
 
-#import <Cocoa/Cocoa.h>
+#include "system_preferences.h"
 
-// FIXME: should be in a header
-void setSystemPreferences();
+#import <Cocoa/Cocoa.h>
 
 void setSystemPreferences() {
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];