Prepare for decoupling analyzer ASTs from element model.

pkg/analysis_server/lib/src/analysis_server.dart

Index: pkg/analysis_server/lib/src/analysis_server.dart
diff --git a/pkg/analysis_server/lib/src/analysis_server.dart b/pkg/analysis_server/lib/src/analysis_server.dart
index da64893198bca5d79093b7da48382b7c8232339e..dd0220c30f76b4282947cda2ca04accfddc0197f 100644
--- a/pkg/analysis_server/lib/src/analysis_server.dart
+++ b/pkg/analysis_server/lib/src/analysis_server.dart
@@ -27,6 +27,7 @@ import 'package:analysis_server/src/services/search/search_engine_internal.dart'
 import 'package:analysis_server/src/services/search/search_engine_internal2.dart';
 import 'package:analysis_server/src/single_context_manager.dart';
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/resolution_accessors.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/exception/exception.dart';
 import 'package:analyzer/file_system/file_system.dart';
@@ -1269,7 +1270,8 @@ class AnalysisServer {
                 sendAnalysisNotificationHighlights(this, file, dartUnit);
                 break;
               case AnalysisService.OUTLINE:
-                AnalysisContext context = dartUnit.element.context;
+                AnalysisContext context =
+                    elementForCompilationUnit(dartUnit).context;
                 LineInfo lineInfo = context.getLineInfo(source);
                 SourceKind kind = context.getKindOf(source);
                 sendAnalysisNotificationOutline(