Implement mac support for having multiple Dart_Port's registered on one OS socket

runtime/bin/eventhandler_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/eventhandler.h"
 #include "bin/eventhandler_linux.h"
 
@@ skipping 124 matching lines @@
 }
 
 
 void EventHandlerImplementation::UpdateEpollInstance(intptr_t old_mask,
                                                      DescriptorInfo *di) {
   intptr_t new_mask = di->Mask();
   if (old_mask != 0 && new_mask == 0) {
     RemoveFromEpollInstance(epoll_fd_, di);
   } else if (old_mask == 0 && new_mask != 0) {
     AddToEpollInstance(epoll_fd_, di);
-  } else if (old_mask != 0 && new_mask != 0) {
-    if (di->IsListeningSocket()) {
-      ASSERT(old_mask == new_mask);
-    } else {
-      RemoveFromEpollInstance(epoll_fd_, di);
-      AddToEpollInstance(epoll_fd_, di);
-    }
+  } else if (old_mask != 0 && new_mask != 0 && old_mask != new_mask) {
+    ASSERT(!di->IsListeningSocket());
+    RemoveFromEpollInstance(epoll_fd_, di);
+    AddToEpollInstance(epoll_fd_, di);
   }
 }
 
 
 DescriptorInfo* EventHandlerImplementation::GetDescriptorInfo(
     intptr_t fd, bool is_listening) {
   ASSERT(fd >= 0);
   HashMap::Entry* entry = socket_map_.Lookup(
       GetHashmapKeyFromFd(fd), GetHashmapHashFromFd(fd), true);
   ASSERT(entry != NULL);
@@ skipping 252 matching lines @@
 
 uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
   // The hashmap does not support keys with value 0.
   return dart::Utils::WordHash(fd + 1);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)