Add Platform.packageRoot and Platform.executableArguments to dart:io.

sdk/lib/io/platform_impl.dart

Index: sdk/lib/io/platform_impl.dart
diff --git a/sdk/lib/io/platform_impl.dart b/sdk/lib/io/platform_impl.dart
index 94d67b6224718e1806617edca4465fa7acf4a3ef..56a586916d04af66c7179bebb6b0398bb6882291 100644
--- a/sdk/lib/io/platform_impl.dart
+++ b/sdk/lib/io/platform_impl.dart
@@ -11,6 +11,8 @@ class _Platform {
   external static _localHostname();
   external static _executable();
   external static _environment();
+  external static List<String> _executableArguments();
+  external static String _packageRoot();
   external static String _version();
 
   static int get numberOfProcessors => _numberOfProcessors();
@@ -27,6 +29,8 @@ class _Platform {
   }
 
   static String executable = _executable();
+  static String packageRoot = _packageRoot();
+  static List<String> get executableArguments => _executableArguments();
 
   static Map<String, String> get environment {
     var env = _environment();