Bug 1798600 - Use Created() during creation instead of Mapped(). r=nika

This is less of lie and avoids calling Mapped() twice. Once during
SharedMemoryBasic::Create and once during SharedMemoryBasic::Map.

This fixes shmem-mapped giving the appearence of leaking because
of the double counting.

Differential Revision: https://phabricator.services.mozilla.com/D160990

ipc/glue/SharedMemoryBasic_mach.mm

@@ -81,7 +81,7 @@ bool SharedMemoryBasic::Create(size_t size) {
     return false;
   }
 
-  Mapped(size);
+  Created(size);
   return true;
 }