Fix for resynthesis when a part URI is empty.

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/ast/standard_resolution_map.dart';
 import 'package:analyzer/dart/constant/value.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 10084 matching lines @@
       checkElementText(
           library,
           r'''
 class C {
   dynamic set x(dynamic this.x) {}
 }
 ''');
     }
   }
 
+  test_invalidUri_part_emptyUri() {
+    allowMissingFiles = true;
+    var library = checkLibrary(r'''
+part '';
+class B extends A {}
+''');
+    if (isStrongMode) {
+      checkElementText(
+          library,
+          r'''
+class B {
+}
+''');
+    } else {
+      checkElementText(
+          library,
+          r'''
+class B {
+}
+''');
+    }
+  }
+
   test_invalidUris() {
     allowMissingFiles = true;
     var library = checkLibrary(r'''
 import '[invalid uri]';
 import '[invalid uri]:foo.dart';
 import 'a1.dart';
 import '[invalid uri]';
 import '[invalid uri]:foo.dart';
 
 export '[invalid uri]';
@@ skipping 4919 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }