Reland "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 fcc8cc9a1fa671a554b15e60531fe35bcb8cf7d1..d21184cc07eff9ce9d47cf452a886c17b10c27ca 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();
 }