Don't refcount tracking id -> slot id mapping.

ui/events/cocoa/events_mac.mm

Index: ui/events/cocoa/events_mac.mm
diff --git a/ui/events/cocoa/events_mac.mm b/ui/events/cocoa/events_mac.mm
index 99d391645730a79dde870c18b9a3e2606377451b..b81114c2c82a099ecc60e7d65c9d7f5865c6d1e4 100644
--- a/ui/events/cocoa/events_mac.mm
+++ b/ui/events/cocoa/events_mac.mm
@@ -160,10 +160,6 @@ void ReleaseCopiedNativeEvent(const base::NativeEvent& event) {
   [event release];
 }
 
-void IncrementTouchIdRefCount(const base::NativeEvent& native_event) {
-  NOTIMPLEMENTED();
-}
-
 void ClearTouchIdIfReleased(const base::NativeEvent& native_event) {
   NOTIMPLEMENTED();
 }