dart:io | Add FileSystemEntity.stat() and FileStat class.

sdk/lib/_internal/compiler/implementation/lib/io_patch.dart

Index: sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
index a31da5738fe96537e69b873c6284d248dc083b67..bc7ea7516a90500b3ba286b0c27a0a7824ac18a5 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
@@ -56,6 +56,12 @@ patch class _FileUtils {
   }
 }
 
+patch class FileStat {
+  patch static List<int> _statSync(String path) {
+    throw new UnsupportedError("FileStat.stat");
+  }
+}
+
 patch class FileSystemEntity {
   patch static _getType(String path, bool followLinks) {
     throw new UnsupportedError("FileSystemEntity._getType");