When recording the type of a captured variable/parameter, use the closure field it maps to. Otherwi…

sdk/lib/_internal/compiler/implementation/elements/elements.dart

 // Copyright (c) 2012, 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 elements;
 
 import 'dart:uri';
 
 import 'modelx.dart';
 import '../tree/tree.dart';
@@ skipping 180 matching lines @@
   bool isGenerativeConstructorBody();
   bool isCompilationUnit();
   bool isClass();
   bool isPrefix();
   bool isVariable();
   bool isParameter();
   bool isStatement();
   bool isTypedef();
   bool isTypeVariable();
   bool isField();
+  bool isFieldParameter();
   bool isAbstractField();
   bool isGetter();
   bool isSetter();
   bool isAccessor();
   bool isLibrary();
   bool isErroneous();
   bool isAmbiguous();
 
   bool isTopLevel();
   bool isAssignable();
@@ skipping 695 matching lines @@
   int get resolutionState;
   Token get beginToken;
   Token get endToken;
 
   // TODO(kasperl): Try to get rid of these.
   void set annotatedElement(Element value);
   void set resolutionState(int value);
 
   MetadataAnnotation ensureResolved(Compiler compiler);
 }