Use GLB for function parameters when doing LUB in strong mode.

pkg/analyzer/lib/src/dart/element/element.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.src.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2721 matching lines @@
    * Initialize a newly created function element to have the given [name].
    */
   FunctionElementImpl.forNode(Identifier name) : super.forNode(name);
 
   /**
    * Initialize a newly created function element to have no name and the given
    * [offset]. This is used for function expressions, that have no name.
    */
   FunctionElementImpl.forOffset(int nameOffset) : super("", nameOffset);
 
+  /**
+   * Synthesize an unnamed function element that takes [parameters] and returns
+   * [returnType].
+   */
+  FunctionElementImpl.synthetic(
+      List<ParameterElement> parameters, DartType returnType)
+      : super("", -1) {
+    synthetic = true;
+    this.returnType = returnType;
+    this.parameters = parameters;
+
+    type = new FunctionTypeImpl(this);
+  }
+
   @override
   String get identifier {
     String identifier = super.identifier;
     if (!isStatic) {
       identifier += "@$nameOffset";
     }
     return identifier;
   }
 
   @override
@@ skipping 2170 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }