- Ensure to patch all newly added external methods in dart2js.

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 350ab9693224ccc5ae0bd87470dca023b1085c95..e4038448bfb9637448f6f65e8241eb76b598e1bf 100644
--- a/sdk/lib/_internal/js_runtime/lib/io_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/io_patch.dart
@@ -420,6 +420,11 @@ class SecurityContext {
   static SecurityContext get defaultContext {
     throw new UnsupportedError("default SecurityContext getter");
   }
+
+  @patch
+  static bool get alpnSupported {
+    throw new UnsupportedError("SecurityContext alpnSupported getter");
+  }
 }
 
 @patch