Fix DDC patch

pkg/dev_compiler/tool/input_sdk/patch/io_patch.dart

Index: pkg/dev_compiler/tool/input_sdk/patch/io_patch.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/patch/io_patch.dart b/pkg/dev_compiler/tool/input_sdk/patch/io_patch.dart
index f79da5c8ab8d501a505fa05e5a112b320063f98e..35d314fcd7d1676e030784d78014c1f1424dee8f 100644
--- a/pkg/dev_compiler/tool/input_sdk/patch/io_patch.dart
+++ b/pkg/dev_compiler/tool/input_sdk/patch/io_patch.dart
@@ -218,6 +218,10 @@ class _Platform {
   static String _version() {
     throw new UnsupportedError("Platform._version");
   }
+  @patch
+  static _ansiSupported() {
+    throw new UnsupportedError("Platform._ansiSupported");
+  }
 }
 
 @patch