Add FunctionElement.hasFunctionSignature.

dart/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 '../constants/expressions.dart';
 import '../tree/tree.dart';
 import '../util/util.dart';
@@ skipping 1114 matching lines @@
   /// element.
   AbstractFieldElement get abstractField;
 
   /// Do not use [computeSignature] outside of the resolver; instead retrieve
   /// the signature through the [functionSignature] field.
   /// Trying to access a function signature that has not been computed in
   /// resolution is an error and calling [computeSignature] covers that error.
   /// This method will go away!
   // TODO(johnniwinther): Rename to `ensureFunctionSignature`.
   @deprecated FunctionSignature computeSignature(Compiler compiler);
+
+  bool get hasFunctionSignature;
 }
 
 /// A top level, static or instance function.
 abstract class MethodElement extends FunctionElement
     implements MemberElement {
 }
 
 /// A local function or closure (anonymous local function).
 abstract class LocalFunctionElement extends FunctionElement
     implements LocalElement {
@@ skipping 414 matching lines @@
   bool get isDeclaredByField;
 
   /// Returns `true` if this member is abstract.
   bool get isAbstract;
 
   /// If abstract, [implementation] points to the overridden concrete member,
   /// if any. Otherwise [implementation] points to the member itself.
   Member get implementation;
 }