Restructure the public API for server

pkg/analysis_server/lib/edit/fix/fix_dart.dart

-// Copyright (c) 2015, 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 analysis_server.edit.fix.fix_dart;
-
-import 'package:analysis_server/edit/fix/fix_core.dart';
-import 'package:analyzer/file_system/file_system.dart';
-import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/engine.dart';
-import 'package:analyzer/src/generated/error.dart';
-import 'package:analyzer/src/generated/source.dart';
-
-/**
- * A [FixContributor] that can be used to contribute fixes for errors in Dart
- * files.
- *
- * Clients are expected to extend this class when implementing plugins.
- */
-abstract class DartFixContributor extends FixContributor {
-  @override
-  List<Fix> computeFixes(ResourceProvider resourceProvider,
-      AnalysisContext context, AnalysisError error) {
-    Source source = error.source;
-    if (!AnalysisEngine.isDartFileName(source.fullName)) {
-      return Fix.EMPTY_LIST;
-    }
-    List<Source> libraries = context.getLibrariesContaining(source);
-    if (libraries.isEmpty) {
-      return Fix.EMPTY_LIST;
-    }
-    CompilationUnit unit =
-        context.resolveCompilationUnit2(source, libraries[0]);
-    if (unit == null) {
-      return Fix.EMPTY_LIST;
-    }
-    return internalComputeFixes(resourceProvider, unit, error);
-  }
-
-  /**
-   * Return a list of fixes for the given [error]. The error was reported
-   * against the given compilation [unit].
-   */
-  List<Fix> internalComputeFixes(ResourceProvider resourceProvider,
-      CompilationUnit unit, AnalysisError error);
-}