Fix listening for multiple signals.

runtime/bin/process_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/process.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 685 matching lines @@
     }
     int status = sigaction(signal, &act, NULL);
     if (status < 0) {
       int err = errno;
       VOID_TEMP_FAILURE_RETRY(close(fds[0]));
       VOID_TEMP_FAILURE_RETRY(close(fds[1]));
       errno = err;
       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) {
   ThreadSignalBlocker blocker(kSignalsCount, kSignals);
   MutexLocker lock(signal_mutex);
   SignalInfo* handler = signal_handlers;
   bool unlisten = true;
   while (handler != NULL) {
@@ skipping 16 matching lines @@
     bzero(&act, sizeof(act));
     act.sa_handler = SIG_DFL;
     sigaction(signal, &act, NULL);
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)