Add MemberEntity.isAbstract and use MemberEntity in function_set.dart

pkg/compiler/lib/src/kernel/elements.dart

 // Copyright (c) 2017, 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.
 
 /// Entity model for elements derived from Kernel IR.
 
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 
 class KLibrary implements LibraryEntity {
@@ skipping 38 matching lines @@
 
   String get name => _name.text;
 
   @override
   bool get isAssignable => false;
 
   @override
   bool get isConst => false;
 
   @override
+  bool get isAbstract => false;
+
+  @override
   bool get isSetter => false;
 
   @override
   bool get isGetter => false;
 
   @override
   bool get isFunction => false;
 
   @override
   bool get isField => false;
@@ skipping 67 matching lines @@
             isExternal: isExternal, isConst: isConst);
 
   @override
   bool get isFactoryConstructor => true;
 
   @override
   bool get isGenerativeConstructor => false;
 }
 
 class KMethod extends KFunction {
+  final bool isAbstract;
+
   KMethod(int memberIndex, KLibrary library, KClass enclosingClass, Name name,
-      {bool isStatic, bool isExternal})
+      {bool isStatic, bool isExternal, this.isAbstract})
       : super(memberIndex, library, enclosingClass, name,
             isStatic: isStatic, isExternal: isExternal);
 
   @override
   bool get isFunction => true;
 
   String get _kind => 'method';
 }
 
 class KGetter extends KFunction {
+  final bool isAbstract;
+
   KGetter(int memberIndex, KLibrary library, KClass enclosingClass, Name name,
-      {bool isStatic, bool isExternal})
+      {bool isStatic, bool isExternal, this.isAbstract})
       : super(memberIndex, library, enclosingClass, name,
             isStatic: isStatic, isExternal: isExternal);
 
   @override
   bool get isGetter => true;
 
   String get _kind => 'getter';
 }
 
 class KSetter extends KFunction {
+  final bool isAbstract;
+
   KSetter(int memberIndex, KLibrary library, KClass enclosingClass, Name name,
-      {bool isStatic, bool isExternal})
+      {bool isStatic, bool isExternal, this.isAbstract})
       : super(memberIndex, library, enclosingClass, name,
             isStatic: isStatic, isExternal: isExternal);
 
   @override
   bool get isAssignable => true;
 
   @override
   bool get isSetter => true;
 
   String get _kind => 'setter';
@@ skipping 26 matching lines @@
 class KLocalFunction implements Local {
   final String name;
   final MemberEntity memberContext;
   final Entity executableContext;
 
   KLocalFunction(this.name, this.memberContext, this.executableContext);
 
   String toString() =>
       'local_function(${memberContext.name}.${name ?? '<anonymous>'})';
 }