Support runtime check of function types.

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

Index: sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart b/sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart
index ac14c322a98fc27e80307b78b9beacdb3bf1bda3..4090bd7341ca984bdb4f98414a0f0f893570c717 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/foreign_helper.dart
@@ -156,3 +156,39 @@ String JS_OPERATOR_IS_PREFIX() {}
  * Returns the prefix used for generated type argument substitutions on classes.
  */
 String JS_OPERATOR_AS_PREFIX() {}
+
+/// Returns the name used for generated function types on classes and methods.
+String JS_SIGNATURE_NAME() {}
+
+/// Returns the name used to tag function type representations in JavaScript.
+String JS_FUNCTION_TYPE_TAG() {}
+
+/**
+ * Returns the name used to tag void return in function type representations
+ * in JavaScript.
+ */
+String JS_FUNCTION_TYPE_VOID_RETURN_TAG() {}
+
+/**
+ * Returns the name used to tag return types in function type representations
+ * in JavaScript.
+ */
+String JS_FUNCTION_TYPE_RETURN_TYPE_TAG() {}
+
+/**
+ * Returns the name used to tag required parameters in function type
+ * representations in JavaScript.
+ */
+String JS_FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG() {}
+
+/**
+ * Returns the name used to tag optional parameters in function type
+ * representations in JavaScript.
+ */
+String JS_FUNCTION_TYPE_OPTIONAL_PARAMETERS_TAG() {}
+
+/**
+ * Returns the name used to tag named parameters in function type
+ * representations in JavaScript.
+ */
+String JS_FUNCTION_TYPE_NAMED_PARAMETERS_TAG() {}