Revert "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 e573b3d39ef05ac3c89369666f9bddd6b6cc588a..51e088fd184912e17b64f9fad1ed52c7fefbc1cc 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
@@ -512,7 +512,7 @@ class AstBuilder extends ScopeListener {
     FormalParameter node;
     if (thisKeyword == null) {
       node = ast.simpleFormalParameter(
-          null, null, null, toAnalyzerToken(keyword), type, name);
+          null, null, toAnalyzerToken(keyword), type, name);
     } else {
       // TODO(scheglov): Ideally the period token should be passed in.
       Token period = identical('.', thisKeyword.next?.stringValue)
@@ -523,7 +523,6 @@ class AstBuilder extends ScopeListener {
       node = ast.fieldFormalParameter(
           null,
           null,
-          null,
           toAnalyzerToken(keyword),
           type,
           toAnalyzerToken(thisKeyword),