Add exitCode getter counterpart to the existing setter in dart:io.

sdk/lib/io/process.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 // TODO(ager): The only reason for this class is that we
 // cannot patch a top-level at this point.
 class _ProcessUtils {
   external static void _exit(int status);
   external static void _setExitCode(int status);
+  external static int _getExitCode();
   external static void _sleep(int millis);
   external static int _pid(Process process);
   external static Stream<ProcessSignal> _watchSignal(ProcessSignal signal);
 }
 
 /**
  * Exit the Dart VM process immediately with the given exit code.
  *
  * This does not wait for any asynchronous operations to terminate. Using
  * [exit] is therefore very likely to lose data.
@@ skipping 20 matching lines @@
  * cross-platform issues.
  */
 void exit(int code) {
   if (code is !int) {
     throw new ArgumentError("Integer value for exit code expected");
   }
   _ProcessUtils._exit(code);
 }
 
 /**
- * Global exit code for the Dart VM.
+ * Set the global exit code for the Dart VM.
+ *
+ * The exit code is global for the Dart VM and the last assignment to
+ * exitCode from any isolate determines the exit code of the Dart VM
+ * on normal termination.
+ *
+ * Default value is `0`.
+ *
+ * See [exit] for more information on how to chose a value for the
+ * exit code.
+ */
+void set exitCode(int code) {
+  if (code is !int) {
+    throw new ArgumentError("Integer value for exit code expected");
+  }
+  _ProcessUtils._setExitCode(code);
+}
+
+/*
+ * Get the global exit code for the Dart VM.
  *
  * The exit code is global for the Dart VM and the last assignment to
  * exitCode from any isolate determines the exit code of the Dart VM
  * on normal termination.
  *
  * See [exit] for more information on how to chose a value for the
  * exit code.
  */
-set exitCode(int code) {
-  if (code is !int) {
-    throw new ArgumentError("Integer value for exit code expected");
-  }
-  _ProcessUtils._setExitCode(code);
-}
+int get exitCode => _ProcessUtils._getExitCode();
 
 /**
  * Sleep for the duration specified in [duration].
  *
  * Use this with care, as no asynchronous operations can be processed
  * in a isolate while it is blocked in a [sleep] call.
  */
 void sleep(Duration duration) {
   int milliseconds = duration.inMilliseconds;
   if (milliseconds < 0) {
@@ skipping 414 matching lines @@
   final int errorCode;
 
   const ProcessException(this.executable, this.arguments, [this.message = "",
                          this.errorCode = 0]);
   String toString() {
     var msg = (message == null) ? 'OS error code: $errorCode' : message;
     var args = arguments.join(' ');
     return "ProcessException: $msg\n  Command: $executable $args";
   }
 }