Change Process.kill to return a boolean instead of throwing an exception when kill fails.

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 533 matching lines @@
   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 signal) {
-  int result = TEMP_FAILURE_RETRY(kill(id, signal));
-  if (result == -1) {
-    return false;
-  }
-  return true;
+  return (TEMP_FAILURE_RETRY(kill(id, signal)) != -1);
 }
 
 
 void Process::TerminateExitCodeHandler() {
   ExitCodeHandler::TerminateExitCodeThread();
 }
 
 
 intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(getpid());
 }