Make use of test_flushAstStructures in analysis server.

pkg/analysis_server/test/analysis/update_content_test.dart

Index: pkg/analysis_server/test/analysis/update_content_test.dart
diff --git a/pkg/analysis_server/test/analysis/update_content_test.dart b/pkg/analysis_server/test/analysis/update_content_test.dart
index e137ab99d63b994bbb48797bc7f427c3471f5689..b8c313d34fa07ed4a138540df0ee0ac51b3136ed 100644
--- a/pkg/analysis_server/test/analysis/update_content_test.dart
+++ b/pkg/analysis_server/test/analysis/update_content_test.dart
@@ -205,7 +205,7 @@ f() {}
     await server.onAnalysisComplete;
     // clear errors and make a no-op change
     filesErrors.clear();
-    server.test_flushResolvedUnit(testFile);
+    server.test_flushAstStructures(testFile);
     server.updateContent('2', {
       testFile: new ChangeContentOverlay([new SourceEdit(0, 4, 'main')])
     });