rework completion request resolve imports

pkg/analysis_server/lib/src/provisional/completion/dart/completion_dart.dart

Index: pkg/analysis_server/lib/src/provisional/completion/dart/completion_dart.dart
diff --git a/pkg/analysis_server/lib/src/provisional/completion/dart/completion_dart.dart b/pkg/analysis_server/lib/src/provisional/completion/dart/completion_dart.dart
index 2d42cbbea6111168429aa7b8310aa7ef32fe23fa..434ae632dc141c7b65806008b910674e2cf3f790 100644
--- a/pkg/analysis_server/lib/src/provisional/completion/dart/completion_dart.dart
+++ b/pkg/analysis_server/lib/src/provisional/completion/dart/completion_dart.dart
@@ -107,16 +107,6 @@ abstract class DartCompletionRequest extends CompletionRequest {
   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
@@ -127,6 +117,16 @@ abstract class DartCompletionRequest extends CompletionRequest {
   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