Code Completion API fix of mistake in DartCompletionRequest

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 27a491520b1061ba121cca6048db254be0d6ee05..97a162ed166db9f5bbd3a6560efe0935a627b742 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
@@ -115,7 +115,7 @@ abstract class DartCompletionRequest extends CompletionRequest {
    * Any information obtained from [target] prior to calling this method
    * should be discarded as it may have changed.
    */
-  Future resolveContainingExpression(Expression expression);
+  Future resolveContainingExpression(AstNode node);
 
   /**
    * Return a [Future] that completes when the element associated with
@@ -125,7 +125,7 @@ abstract class DartCompletionRequest extends CompletionRequest {
    * Any information obtained from [target] prior to calling this method
    * should be discarded as it may have changed.
    */
-  Future resolveContainingStatement(Statement expression);
+  Future resolveContainingStatement(AstNode node);
 
   /**
      * Return a [Future] that completes with a list of [ImportElement]s