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

runtime/bin/process.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/dartutils.h"
 #include "bin/process.h"
 
 #include "include/dart_api.h"
 
 // Extract an array of C strings from a list of Dart strings.
@@ skipping 129 matching lines @@
   delete[] string_args;
   delete[] string_environment;
   Dart_SetReturnValue(args, Dart_NewBoolean(error_code == 0));
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(Process_Kill)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t pid = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 1));
-  bool success = Process::Kill(pid);
+  int signal = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 2));
+  bool success = Process::Kill(pid, signal);
   Dart_SetReturnValue(args, Dart_NewBoolean(success));
   Dart_ExitScope();
 }