Fix summary resynthesis in the event of a self-import.

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

 // Copyright (c) 2016, 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 analyzer.test.src.summary.resynthesize_ast_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart'
@@ skipping 599 matching lines @@
   }
 }
 
 @reflectiveTest
 class ResynthesizeAstTest extends ResynthesizeTest
     with _AstResynthesizeTestMixin {
   @override
   bool get checkPropagatedTypes => false;
 
   @override
-  void checkLibrary(String text,
+  LibraryElementImpl checkLibrary(String text,
       {bool allowErrors: false, bool dumpSummaries: false}) {
     Source source = addTestSource(text);
     LibraryElementImpl resynthesized = _encodeDecodeLibraryElement(source);
     LibraryElementImpl original = context.computeLibraryElement(source);
     checkLibraryElements(original, resynthesized);
+    return resynthesized;
   }
 
   @override
   DartSdk createDartSdk() => AbstractContextTest.SHARED_MOCK_SDK;
 
   @override
   TestSummaryResynthesizer encodeDecodeLibrarySource(Source source) {
     return _encodeLibrary(source);
   }
 
@@ skipping 153 matching lines @@
     }
 
     UnlinkedUnit definingUnit = _getUnlinkedUnit(librarySource);
     LinkedLibraryBuilder linkedLibrary =
         prelink(definingUnit, getPart, getImport);
     linkedLibrary.dependencies.skip(1).forEach((LinkedDependency d) {
       _serializeLibrary(resolveRelativeUri(d.uri));
     });
   }
 }