Audit all of sky's system <> style includes

sky/engine/core/editing/TextAffinity.h

Index: sky/engine/core/editing/TextAffinity.h
diff --git a/sky/engine/core/editing/TextAffinity.h b/sky/engine/core/editing/TextAffinity.h
index d3effaa58d77f9fdcd71c3456b35b10488a1312c..e31878f65a0b3378572f2fa508674ac16ec10087 100644
--- a/sky/engine/core/editing/TextAffinity.h
+++ b/sky/engine/core/editing/TextAffinity.h
@@ -26,13 +26,9 @@
 #ifndef TextAffinity_h
 #define TextAffinity_h
 
-#ifdef __OBJC__
-#include <AppKit/NSTextView.h>
-#endif
-
 namespace blink {
 
-// These match the AppKit values for these concepts.
+// Historically these matched the AppKit values for these concepts.
 // From NSTextView.h:
 // NSSelectionAffinityUpstream = 0
 // NSSelectionAffinityDownstream = 1
@@ -40,18 +36,4 @@ enum EAffinity { UPSTREAM = 0, DOWNSTREAM = 1 };
 
 } // namespace blink
 
-#ifdef __OBJC__
-
-inline NSSelectionAffinity kit(blink::EAffinity affinity)
-{
-    return static_cast<NSSelectionAffinity>(affinity);
-}
-
-inline blink::EAffinity core(NSSelectionAffinity affinity)
-{
-    return static_cast<blink::EAffinity>(affinity);
-}
-
-#endif
-
 #endif // TextAffinity_h