Fix static modifier for synthetic fields coming from summaries.

pkg/analyzer/test/src/summary/resynthesize_common.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 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/constant/value.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 1241 matching lines @@
       }
       return false;
     } else if (modifier == Modifier.SETTER) {
       if (element is PropertyAccessorElement) {
         return element.isSetter;
       }
       return false;
     } else if (modifier == Modifier.STATIC) {
       if (element is ExecutableElement) {
         return element.isStatic;
+      } else if (element is FieldElement) {
+        return element.isStatic;
       }
       return false;
     } else if (modifier == Modifier.SYNTHETIC) {
       return element.isSynthetic;
     }
     throw new UnimplementedError(
         'Modifier $modifier for ${element?.runtimeType}');
   }
 }
 
@@ skipping 3431 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }