Fix listening for multiple signals.

runtime/bin/process_macos.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_MACOS)
 
 #include "bin/process.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 738 matching lines @@
     for (int i = 0; i < kSignalsCount; i++) {
       sigaddset(&act.sa_mask, kSignals[i]);
     }
     intptr_t status = NO_RETRY_EXPECTED(sigaction(signal, &act, NULL));
     if (status < 0) {
       VOID_TEMP_FAILURE_RETRY(close(fds[0]));
       VOID_TEMP_FAILURE_RETRY(close(fds[1]));
       return -1;
     }
   }
-  if (signal_handlers == NULL) {
-    signal_handlers = new SignalInfo(fds[1], signal);
-  } else {
-    new SignalInfo(fds[1], signal, signal_handlers);
-  }
+  signal_handlers = new SignalInfo(fds[1], signal, signal_handlers);
   return fds[0];
 }
 
 
 void Process::ClearSignalHandler(intptr_t signal) {
   signal = SignalMap(signal);
   if (signal == -1) return;
   ThreadSignalBlocker blocker(kSignalsCount, kSignals);
   MutexLocker lock(signal_mutex);
   SignalInfo* handler = signal_handlers;
@@ skipping 18 matching lines @@
     bzero(&act, sizeof(act));
     act.sa_handler = SIG_DFL;
     VOID_NO_RETRY_EXPECTED(sigaction(signal, &act, NULL));
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)