Add an AST factory method for fieldDeclaration with all optional named parameters.

pkg/analyzer/lib/src/dart/ast/ast_factory.dart

Index: pkg/analyzer/lib/src/dart/ast/ast_factory.dart
diff --git a/pkg/analyzer/lib/src/dart/ast/ast_factory.dart b/pkg/analyzer/lib/src/dart/ast/ast_factory.dart
index f7e92be807ebd241ee06786c8f05312099177bde..a3a09ee9dae9ca82b2d55be724169fa828473cc9 100644
--- a/pkg/analyzer/lib/src/dart/ast/ast_factory.dart
+++ b/pkg/analyzer/lib/src/dart/ast/ast_factory.dart
@@ -361,7 +361,18 @@ class AstFactoryImpl extends AstFactory {
           VariableDeclarationList fieldList,
           Token semicolon) =>
       new FieldDeclarationImpl(
-          comment, metadata, staticKeyword, fieldList, semicolon);
+          comment, metadata, null, staticKeyword, fieldList, semicolon);
+
+  @override
+  FieldDeclaration fieldDeclaration2(
+          {Comment comment,
+          List<Annotation> metadata,
+          Token covariantKeyword,
+          Token staticKeyword,
+          @required VariableDeclarationList fieldList,
+          @required Token semicolon}) =>
+      new FieldDeclarationImpl(comment, metadata, covariantKeyword,
+          staticKeyword, fieldList, semicolon);
 
   @override
   FieldFormalParameter fieldFormalParameter(