Reland "Introduce optional 'bool shared' parameter to ServerSocket.bind() ..."

dart/runtime/bin/eventhandler_macos.cc

Index: dart/runtime/bin/eventhandler_macos.cc
diff --git a/dart/runtime/bin/eventhandler_macos.cc b/dart/runtime/bin/eventhandler_macos.cc
index 6caadc09622776e84c070dfddb4a2a5f7ef2e33d..fa2dbf6cd9dde328a680cf0fde3165bdfb40b85b 100644
--- a/dart/runtime/bin/eventhandler_macos.cc
+++ b/dart/runtime/bin/eventhandler_macos.cc
@@ -241,18 +241,18 @@ void EventHandlerImplementation::HandleInterruptFd() {
           // We only close the socket file descriptor from the operating
           // system if there are no other dart socket objects which
           // are listening on the same (address, port) combination.
+          ListeningSocketRegistry *registry =
+              ListeningSocketRegistry::Instance();
 
-          // TODO(dart:io): This assumes that all sockets listen before we
-          // close.
-          // This needs to be synchronized with a global datastructure.
-          if (new_mask == 0) {
-            socket_map_.Remove(
-                GetHashmapKeyFromFd(fd), GetHashmapHashFromFd(fd));
+          MutexLocker locker(registry->mutex());
+
+          if (registry->CloseSafe(fd)) {
+            ASSERT(new_mask == 0);
+            socket_map_.Remove(GetHashmapKeyFromFd(fd),
+                               GetHashmapHashFromFd(fd));
             di->Close();
             delete di;
           }
-
-
         } else {
           ASSERT(new_mask == 0);
           socket_map_.Remove(