Replace computeNode() with AstProvider in search.

pkg/analyzer/lib/src/dart/analysis/ast_provider_driver.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
@@ skipping 48 matching lines @@
       if (element.enclosingElement is ClassElement) {
         return nameNode.getAncestor((node) => node is MethodDeclaration);
       } else if (element.enclosingElement is CompilationUnitElement) {
         return nameNode.getAncestor((node) => node is FunctionDeclaration);
       }
       return null;
     }
     if (element is TopLevelVariableElement) {
       return nameNode.getAncestor((node) => node is VariableDeclaration);
     }
-    return null;
+    return nameNode;
   }
 
   @override
   Future<T> getParsedNodeForElement<T extends AstNode>(Element element) async {
     CompilationUnit unit = await getParsedUnitForElement(element);
     return findNodeForElement(unit, element) as T;
   }
 
   @override
   Future<T> getResolvedNodeForElement<T extends AstNode>(
@@ skipping 18 matching lines @@
     return parseResult.unit;
   }
 
   @override
   Future<CompilationUnit> getResolvedUnitForElement(Element element) async {
     String path = element.source.fullName;
     AnalysisResult analysisResult = await driver.getResult(path);
     return analysisResult?.unit;
   }
 }