dart2js: Remove obsolete shortcut code in function-type checking.

sdk/lib/_internal/compiler/js_lib/js_rti.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * This part contains helpers for supporting runtime type information.
  *
  * The helper use a mixture of Dart and JavaScript objects. To indicate which is
  * used where we adopt the scheme of using explicit type annotation for Dart
  * objects and 'var' or omitted return type for JavaScript objects.
@@ skipping 382 matching lines @@
   if (rti != null) {
     // If the type has type variables (that is, `rti != null`), make a copy of
     // the type arguments and insert [o] in the first position to create a
     // compound type representation.
     rti = JS('JSExtendableArray', '#.slice()', rti);  // Make a copy.
     JS('', '#.splice(0, 0, #)', rti, type);  // Insert type at position 0.
     type = rti;
   } else if (hasField(t, '${JS_FUNCTION_TYPE_TAG()}')) {
     // Functions are treated specially and have their type information stored
     // directly in the instance.
-    var signatureName =
-        '${JS_OPERATOR_IS_PREFIX()}_${getField(t, JS_FUNCTION_TYPE_TAG())}';
-    if (hasField(o, signatureName)) return true;
     var targetSignatureFunction = getField(o, '${JS_SIGNATURE_NAME()}');
     if (targetSignatureFunction == null) return false;
     type = invokeOn(targetSignatureFunction, o, null);
     return isFunctionSubtype(type, t);
   }
   return isSubtype(type, t);
 }
 
 Object subtypeOfRuntimeTypeCast(Object object, var type) {
   if (object != null && !checkSubtypeOfRuntimeType(object, type)) {
@@ skipping 262 matching lines @@
  * `null` and `undefined` (which we can avoid).
  */
 bool isIdentical(var s, var t) => JS('bool', '# === #', s, t);
 
 /**
  * Returns `true` if the JavaScript values [s] and [t] are not identical. We use
  * this helper instead of [identical] because `identical` needs to merge
  * `null` and `undefined` (which we can avoid).
  */
 bool isNotIdentical(var s, var t) => JS('bool', '# !== #', s, t);