Issue 29288. Resynthesize Import/Export/PartElement for every directive.

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

Index: pkg/analyzer/test/src/summary/resynthesize_ast_test.dart
diff --git a/pkg/analyzer/test/src/summary/resynthesize_ast_test.dart b/pkg/analyzer/test/src/summary/resynthesize_ast_test.dart
index 2cb5cc0d8ffd4b23129bb1c95837d581d2a10a64..94691e47093fac9ac41ef5e92248713b96cad5b8 100644
--- a/pkg/analyzer/test/src/summary/resynthesize_ast_test.dart
+++ b/pkg/analyzer/test/src/summary/resynthesize_ast_test.dart
@@ -247,6 +247,8 @@ abstract class _ResynthesizeAstTest extends ResynthesizeTest
     with _AstResynthesizeTestMixin {
   bool get isStrongMode;
 
+  bool get shouldCompareLibraryElements;
+
   @override
   LibraryElementImpl checkLibrary(String text,
       {bool allowErrors: false, bool dumpSummaries: false}) {
@@ -259,7 +261,9 @@ abstract class _ResynthesizeAstTest extends ResynthesizeTest
         fail('Analysis errors: $errors');
       }
     }
-    checkLibraryElements(original, resynthesized);
+    if (shouldCompareLibraryElements) {
+      checkLibraryElements(original, resynthesized);
+    }
     return resynthesized;
   }