Start unraveling circularities between analyzer and front_end/kernel.

pkg/analyzer/lib/src/fasta/mock_element.dart

 // Copyright (c) 2016, 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.
 
 library fasta.analyzer.mock_element;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 
-import '../builder/builder.dart' show Builder;
+import 'package:front_end/src/fasta/builder/builder.dart' show Builder;
 
-import '../errors.dart' show internalError;
+import 'package:front_end/src/fasta/errors.dart' show internalError;
 import 'package:analyzer/src/generated/source.dart';
 
 abstract class MockElement extends Builder implements Element, LocalElement {
   final ElementKind kind;
 
   MockElement(this.kind) : super(null, -1, null);
 
   get librarySource => internalError("not supported.");
 
   get source => internalError("not supported.");
@@ skipping 342 matching lines @@
   get constantValue => internalError("not supported.");
 
   computeConstantValue() => internalError("not supported.");
 
   void appendToWithoutDelimiters(StringBuffer buffer) {
     return internalError("not supported.");
   }
 
   FormalParameter computeNode() => internalError("not supported.");
 }