dart2js cps: Support function types in 'is' and 'as' operators.

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 371 matching lines @@
   var rti = getRuntimeTypeInfo(o);
   o = getInterceptor(o);
   var type = getRawRuntimeType(o);
   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 (isDartFunctionType(t)) {
+  }
+  if (isDartFunctionType(t)) {
     // Functions are treated specially and have their type information stored
     // directly in the instance.
     var targetSignatureFunction =
         getField(o, '${JS_GET_NAME(JsGetName.SIGNATURE_NAME)}');
     if (targetSignatureFunction == null) return false;
     type = invokeOn(targetSignatureFunction, o, null);
     return isFunctionSubtype(type, t);
   }
   return isSubtype(type, t);
 }
@@ skipping 268 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);