Don't use ThreadSignalBlocker in mac eventhandler.

runtime/bin/eventhandler_macos.h

 // 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.
 
 #ifndef BIN_EVENTHANDLER_MACOS_H_
 #define BIN_EVENTHANDLER_MACOS_H_
 
 #if !defined(BIN_EVENTHANDLER_H_)
 #error Do not include eventhandler_macos.h directly; use eventhandler.h instead.
 #endif
@@ skipping 25 matching lines @@
         port_(0),
         mask_(0),
         tracked_by_kqueue_(false),
         tokens_(16) {
     ASSERT(fd_ != -1);
   }
 
   bool HasReadEvent();
   bool HasWriteEvent();
 
-  void Close() {
-    port_ = 0;
-    mask_ = 0;
-    VOID_TEMP_FAILURE_RETRY(close(fd_));
-    fd_ = -1;
-  }
-
   bool IsListeningSocket() { return (mask_ & (1 << kListeningSocket)) != 0; }
 
   void SetPortAndMask(Dart_Port port, intptr_t mask) {
     ASSERT(fd_ != -1);
     port_ = port;
     mask_ = mask;
   }
 
   intptr_t fd() { return fd_; }
   Dart_Port port() { return port_; }
@@ skipping 52 matching lines @@
   TimeoutQueue timeout_queue_;
   bool shutdown_;
   int interrupt_fds_[2];
   int kqueue_fd_;
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_EVENTHANDLER_MACOS_H_