Migrate one file in plugin_server

There are two other files that need to be migrated, but the unmigrated
portions are being used by other unmigrated files, so they can't be
migrated yet.

Change-Id: I1f0d029c16734b1599783149ade5a0d6ec29d349
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/390924
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: bwilkerson

pkg/analysis_server_plugin/analyzer_use_new_elements.txt

@@ -9,6 +9,7 @@ lib/src/correction/dart_change_workspace.dart
 lib/src/correction/fix_generators.dart
 lib/src/correction/fix_in_file_processor.dart
 lib/src/correction/fix_processor.dart
+lib/src/plugin_server.dart
 lib/src/registry.dart
 lib/src/utilities/selection.dart
 test/edit/correction_utils_test.dart

pkg/analysis_server_plugin/lib/src/plugin_server.dart

@@ -220,7 +220,8 @@ class PluginServer {
       return [];
     }
     var listener = RecordingErrorListener();
-    var errorReporter = ErrorReporter(listener, result.libraryElement.source);
+    var errorReporter =
+        ErrorReporter(listener, result.libraryElement2.firstFragment.source);
 
     var currentUnit = LintRuleUnitContext(
       file: result.file,
@@ -244,8 +245,8 @@ class PluginServer {
     var context = LinterContextWithResolvedResults(
       allUnits,
       currentUnit,
-      libraryResult.element.typeProvider,
-      libraryResult.element.typeSystem as TypeSystemImpl,
+      libraryResult.element2.typeProvider,
+      libraryResult.element2.typeSystem as TypeSystemImpl,
       (analysisContext.currentSession as AnalysisSessionImpl)
           .inheritanceManager,
       // TODO(srawlins): Support 'package' parameter.