Revert "Support runtime check of function types."

tests/compiler/dart2js/subtype_test.dart

Index: tests/compiler/dart2js/subtype_test.dart
diff --git a/tests/compiler/dart2js/subtype_test.dart b/tests/compiler/dart2js/subtype_test.dart
index 35a46517582f585d7092c458cbe068ef433df522..b4efe86a379b780bdadbe551b75fd428b963defd 100644
--- a/tests/compiler/dart2js/subtype_test.dart
+++ b/tests/compiler/dart2js/subtype_test.dart
@@ -264,7 +264,6 @@ void testCallableSubtype() {
 
 testFunctionSubtyping() {
   var env = new TypeEnvironment(r"""
-      _() => null;
       void void_() {}
       void void_2() {}
       int int_() => 0;
@@ -286,7 +285,6 @@ testFunctionSubtyping() {
 
 testTypedefSubtyping() {
   var env = new TypeEnvironment(r"""
-      typedef _();
       typedef void void_();
       typedef void void_2();
       typedef int int_();
@@ -319,13 +317,6 @@ functionSubtypingHelper(TypeEnvironment env) {
   // Function <: () -> int
   expect(false, 'Function', 'int_');
 
-  // () -> dynamic <: () -> dynamic
-  expect(true, '_', '_');
-  // () -> dynamic <: () -> void
-  expect(true, '_', 'void_');
-  // () -> void <: () -> dynamic
-  expect(true, 'void_', '_');
-
   // () -> int <: () -> void
   expect(true, 'int_', 'void_');
   // () -> void <: () -> int