rework completion request resolve imports

pkg/analysis_server/lib/src/provisional/completion/dart/completion_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.src.provisional.completion.completion_dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart';
@@ skipping 89 matching lines @@
 
   /**
    * Return the completion target.  This determines what part of the parse tree
    * will receive the newly inserted text.
    * At a minimum, all declarations in the completion scope in [target.unit]
    * will be resolved if they can be resolved.
    */
   CompletionTarget get target;
 
   /**
-   * Return a [Future] that completes with a list of directives for the library
-   * in which in which the completion is occurring.
-   * The [Future] may return `null` if the library unit cannot be determined
-   * (e.g. unlinked part file).
-   * Any information obtained from [target] prior to calling this method
-   * should be discarded as it may have changed.
-   */
-  Future<List<Directive>> resolveDirectives();
-
-  /**
    * Return a [Future] that completes when the element associated with
    * the given [expression] in the target compilation unit is available.
    * It may also complete if the expression cannot be resolved
    * (e.g. unknown identifier, completion aborted, etc).
    * Any information obtained from [target] prior to calling this method
    * should be discarded as it may have changed.
    */
   Future resolveExpression(Expression expression);
 
   /**
+     * Return a [Future] that completes with a list of [ImportElement]s
+     * for the library in which in which the completion is occurring.
+     * The [Future] may return `null` if the library unit cannot be determined
+     * (e.g. unlinked part file).
+     * Any information obtained from [target] prior to calling this method
+     * should be discarded as it may have changed.
+     */
+  Future<List<ImportElement>> resolveImports();
+
+  /**
    * Return a [Future] that completes with a list of [CompilationUnitElement]s
    * comprising the library in which in which the completion is occurring.
    * The [Future] may return `null` if the library unit cannot be determined
    * (e.g. unlinked part file).
    * Any information obtained from [target] prior to calling this method
    * should be discarded as it may have changed.
    */
   Future<List<CompilationUnitElement>> resolveUnits();
 }