[dart:io] Adds functions to set file access and modification time

sdk/lib/_internal/js_runtime/lib/io_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/io_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/io_patch.dart b/sdk/lib/_internal/js_runtime/lib/io_patch.dart
index d941bb23e82efe2e71c13cf405fec292f3bf4dd7..f79da5c8ab8d501a505fa05e5a112b320063f98e 100644
--- a/sdk/lib/_internal/js_runtime/lib/io_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/io_patch.dart
@@ -135,6 +135,18 @@ class _File {
     throw new UnsupportedError("File._lastModified");
   }
   @patch
+  static _lastAccessed(String path) {
+    throw new UnsupportedError("File._lastAccessed");
+  }
+  @patch
+  static _setLastModified(String path, int millis) {
+    throw new UnsupportedError("File._setLastModified");
+  }
+  @patch
+  static _setLastAccessed(String path, int millis) {
+    throw new UnsupportedError("File._setLastAccessed");
+  }
+  @patch
   static _open(String path, int mode) {
     throw new UnsupportedError("File._open");
   }