Issue 27820. Add fix for CompileTimeErrorCode.UNDEFINED_CLASS.

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index aaa21fa30a6033034eab4053a7d54c4d21667bb4..2fab11c4912a31fa856602c6a8369f3d3d95ae52 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -291,7 +291,8 @@ class FixProcessor {
       // implement methods
       _addFix_createMissingOverrides();
     }
-    if (errorCode == StaticWarningCode.CAST_TO_NON_TYPE ||
+    if (errorCode == CompileTimeErrorCode.UNDEFINED_CLASS ||
+        errorCode == StaticWarningCode.CAST_TO_NON_TYPE ||
         errorCode == StaticWarningCode.TYPE_TEST_WITH_UNDEFINED_NAME ||
         errorCode == StaticWarningCode.UNDEFINED_CLASS) {
       _addFix_importLibrary_withType();