Move PackageIndexAssembler into analysis_server.

pkg/analysis_server/lib/src/services/index/index_unit.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.
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/member.dart';
@@ skipping 888 matching lines @@
         usedNameOffsets: nameRelations.map((r) => r.offset).toList(),
         usedNameIsQualifiedFlags:
             nameRelations.map((r) => r.isQualified).toList());
   }
 
   void defineName(String name, IndexNameKind kind, int offset) {
     _StringInfo nameInfo = pkg._getStringInfo(name);
     definedNames.add(new _DefinedNameInfo(nameInfo, kind, offset));
   }
 }