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

sdk/lib/io/process.dart

Index: sdk/lib/io/process.dart
diff --git a/sdk/lib/io/process.dart b/sdk/lib/io/process.dart
index 828145e8304bce61369dd94fedfcd0ba7b80ab04..f90f8baa968b30f58bf195ad4a41bde6087ea840 100644
--- a/sdk/lib/io/process.dart
+++ b/sdk/lib/io/process.dart
@@ -9,6 +9,7 @@ part of dart.io;
 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);
@@ -49,22 +50,36 @@ void exit(int 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.
  */
-set exitCode(int 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.
+ */
+int get exitCode => _ProcessUtils._getExitCode();
+
 /**
  * Sleep for the duration specified in [duration].
  *