dart2js: remove optimization when computing required type checks.

pkg/compiler/lib/src/js_backend/runtime_types.dart

Index: pkg/compiler/lib/src/js_backend/runtime_types.dart
diff --git a/pkg/compiler/lib/src/js_backend/runtime_types.dart b/pkg/compiler/lib/src/js_backend/runtime_types.dart
index f8aa7b15c6a930dd527ffd4505ed05a4db4772ae..eb4616c3695eecac19cf2224fe8ef48d41258651 100644
--- a/pkg/compiler/lib/src/js_backend/runtime_types.dart
+++ b/pkg/compiler/lib/src/js_backend/runtime_types.dart
@@ -257,11 +257,9 @@ class RuntimeTypes {
 
   void computeRequiredChecks() {
     Set<DartType> isChecks = compiler.codegenWorld.isChecks;
-    bool hasFunctionTypeCheck =
-        isChecks.any((type) => identical(type.kind, TypeKind.FUNCTION));
-    Set<DartType> instantiatedTypesAndClosures = hasFunctionTypeCheck
-        ? computeInstantiatedTypesAndClosures(compiler.codegenWorld)
-        : compiler.codegenWorld.instantiatedTypes;
+    // These types are needed for is-checks against function types.
+    Set<DartType> instantiatedTypesAndClosures =
+        computeInstantiatedTypesAndClosures(compiler.codegenWorld);
     computeInstantiatedArguments(instantiatedTypesAndClosures, isChecks);
     computeCheckedArguments(instantiatedTypesAndClosures, isChecks);
     cachedRequiredChecks =