Support runtime check of function types.

sdk/lib/_internal/lib/foreign_helper.dart

Index: sdk/lib/_internal/lib/foreign_helper.dart
diff --git a/sdk/lib/_internal/lib/foreign_helper.dart b/sdk/lib/_internal/lib/foreign_helper.dart
index 3cfe86a429bfeea72fd0c862aa5ad46a357c154b..3e8ac6374c78165acb0f57eaefe8fb9efbd82595 100644
--- a/sdk/lib/_internal/lib/foreign_helper.dart
+++ b/sdk/lib/_internal/lib/foreign_helper.dart
@@ -161,6 +161,9 @@ String JS_OPERATOR_AS_PREFIX() {}
 /// Returns the name of the class `Object` in the generated code.
 String JS_OBJECT_CLASS_NAME() {}
 
+/// Returns the name of the class `Function` in the generated code.
+String JS_FUNCTION_CLASS_NAME() {}
+
 /**
  * Returns the field name used for determining if an object or its
  * interceptor has JavaScript indexing behavior.
@@ -171,3 +174,44 @@ String JS_IS_INDEXABLE_FIELD_NAME() {}
  * Returns the object corresponding to Namer.CURRENT_ISOLATE.
  */
 JS_CURRENT_ISOLATE() {}
+
+/// 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() {}
+
+/**
+ * Returns the global object, usually called encoded as [: $ :].
+ */
+JS_GLOBAL_OBJECT() {}