Add summary support for ShowElementCombinator.end and .offset.

pkg/analyzer/test/src/summary/resynthesize_test.dart

 // Copyright (c) 2015, 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 test.src.serialization.elements_test;
 
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 727 matching lines @@
     // TODO(paulberry): do we need to deal with
     // MultiplyInheritedMethodElementImpl?
     compareExecutableElements(resynthesized, original, desc);
   }
 
   void compareNamespaceCombinators(
       NamespaceCombinator resynthesized, NamespaceCombinator original) {
     if (original is ShowElementCombinatorImpl &&
         resynthesized is ShowElementCombinatorImpl) {
       expect(resynthesized.shownNames, original.shownNames);
+      expect(resynthesized.offset, original.offset);
+      expect(resynthesized.end, original.end);
     } else if (original is HideElementCombinatorImpl &&
         resynthesized is HideElementCombinatorImpl) {
       expect(resynthesized.hiddenNames, original.hiddenNames);
     } else if (resynthesized.runtimeType != original.runtimeType) {
       fail(
           'Type mismatch: expected ${original.runtimeType}, got ${resynthesized.runtimeType}');
     } else {
       fail('Unimplemented comparison for ${original.runtimeType}');
     }
   }
@@ skipping 3195 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }