Give Process.kill an optional argument to specify which signal to send.

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 "bin/process.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <signal.h>
@@ skipping 532 matching lines @@
   TEMP_FAILURE_RETRY(close(write_out[0]));
   FDUtils::SetNonBlocking(read_err[0]);
   *err = read_err[0];
   TEMP_FAILURE_RETRY(close(read_err[1]));
 
   *id = pid;
   return 0;
 }
 
 
-bool Process::Kill(intptr_t id) {
-  int result = TEMP_FAILURE_RETRY(kill(id, SIGKILL));
+bool Process::Kill(intptr_t id, int signal) {
+  int result = TEMP_FAILURE_RETRY(kill(id, signal));
   if (result == -1) {
     return false;
   }
   return true;
 }
 
 
 void Process::TerminateExitCodeHandler() {
   ExitCodeHandler::TerminateExitCodeThread();
 }