- Implement Platform.packageRoot and Platform.packageConfig based

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 6380e0d7c92f622495d3c9ca2149db2baafdfda9..f4d7a247dfa78e0086ff9e91ce6c9e22e7a10106 100644
--- a/sdk/lib/io/platform_impl.dart
+++ b/sdk/lib/io/platform_impl.dart
@@ -29,11 +29,13 @@ class _Platform {
   external static _environment();
   external static List<String> _executableArguments();
   external static String _packageRoot();
+  external static String _packageConfig();
   external static String _version();
 
   static String executable = _executable();
   static String resolvedExecutable = _resolvedExecutable();
   static String packageRoot = _packageRoot();
+  static String packageConfig = _packageConfig();
 
   // Cache the OS environemnt. This can be an OSError instance if
   // retrieving the environment failed.