simplify contributors by resolving declarations in scope

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 658221e3289400f5d60f592d4308025125e555e4..6163a5415cb98ec9c660a03e511f4206e9447959 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
@@ -11,6 +11,7 @@ import 'package:analysis_server/src/provisional/completion/completion_core.dart'
 import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
+import 'package:analyzer/src/generated/source.dart';
 
 export 'package:analysis_server/src/provisional/completion/completion_core.dart'
     show EMPTY_LIST;
@@ -77,6 +78,14 @@ abstract class DartCompletionRequest extends CompletionRequest {
   Future<LibraryElement> get libraryElement;
 
   /**
+   * The source for the library containing the completion request.
+   * This may be different from the source in which the completion is requested
+   * if the completion is being requested in a part file.
+   * This may be `null` if the library for a part file cannot be determined.
+   */
+  Source get librarySource;
+
+  /**
    * Answer the [DartType] for Object in dart:core
    */
   DartType get objectType;
@@ -84,20 +93,12 @@ abstract class DartCompletionRequest extends CompletionRequest {
   /**
    * 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 compilation unit in which
-   * all declarations in all scopes containing [target] have been resolved.
-   * The [Future] may return `null` if the unit cannot be resolved
-   * (e.g. unlinked part file).
-   * Any information obtained from [target] prior to calling this method
-   * should be discarded as it may have changed.
-   */
-  Future<CompilationUnit> resolveDeclarationsInScope();
-
-  /**
    * 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