Add completion tests for the new analysis driver.

pkg/analysis_server/test/services/completion/dart/library_prefix_contributor_test.dart

Index: pkg/analysis_server/test/services/completion/dart/library_prefix_contributor_test.dart
diff --git a/pkg/analysis_server/test/services/completion/dart/library_prefix_contributor_test.dart b/pkg/analysis_server/test/services/completion/dart/library_prefix_contributor_test.dart
index 45d26da97b0c749e33f39a1c30d3e5b0e9376426..cb104978acbe50a24a30b3774718360e2bde801e 100644
--- a/pkg/analysis_server/test/services/completion/dart/library_prefix_contributor_test.dart
+++ b/pkg/analysis_server/test/services/completion/dart/library_prefix_contributor_test.dart
@@ -15,6 +15,7 @@ import 'completion_contributor_util.dart';
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(LibraryPrefixContributorTest);
+    defineReflectiveTests(LibraryPrefixContributorTest_Driver);
   });
 }
 
@@ -375,3 +376,16 @@ main() {new ^ String x = "hello";}''');
     assertNoSuggestions();
   }
 }
+
+@reflectiveTest
+class LibraryPrefixContributorTest_Driver extends LibraryPrefixContributorTest {
+  @override
+  bool get enableNewAnalysisDriver => true;
+
+  @failingTest
+  @override
+  test_InstanceCreationExpression_inPart() {
+    // Bad state: Should not be used with the new analysis driver.
+    return super.test_InstanceCreationExpression_inPart();
+  }
+}