Add NormalFormalParameter.covariantKeyword setter and factory parameter.

pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart

Index: pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
index e357b9cd89b35ee2837b266d4da765d16f653bb0..533ef035d361858e503eb5bdd8561f6eefb6e372 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
@@ -506,7 +506,7 @@ class AstBuilder extends ScopeListener {
     FormalParameter node;
     if (thisKeyword == null) {
       node = ast.simpleFormalParameter(
-          null, null, toAnalyzerToken(keyword), type, name);
+          null, null, null, toAnalyzerToken(keyword), type, name);
     } else {
       // TODO(scheglov): Ideally the period token should be passed in.
       Token period = identical('.', thisKeyword.next?.stringValue)
@@ -517,6 +517,7 @@ class AstBuilder extends ScopeListener {
       node = ast.fieldFormalParameter(
           null,
           null,
+          null,
           toAnalyzerToken(keyword),
           type,
           toAnalyzerToken(thisKeyword),