Add an interface for request parameters

pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart

Index: pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
diff --git a/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart b/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
index 285f0961cb818389354d4a6501e1e77faf770af1..643e47808e352a3b0d2ec741f76a79a2d8158fe2 100644
--- a/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
+++ b/pkg/analyzer_plugin/tool/spec/codegen_dart_protocol.dart
@@ -223,6 +223,8 @@ class CodegenProtocolVisitor extends DartCodegenVisitor with CodeGenerator {
       writeln(' extends RefactoringFeedback implements HasToJson {');
     } else if (impliedType.kind == 'refactoringOptions') {
       writeln(' extends RefactoringOptions implements HasToJson {');
+    } else if (impliedType.kind == 'requestParams') {
+      writeln(' implements RequestParams {');
     } else if (impliedType.kind == 'requestResult') {
       writeln(' implements ResponseResult {');
     } else {
@@ -405,6 +407,8 @@ class CodegenProtocolVisitor extends DartCodegenVisitor with CodeGenerator {
       writeln(' extends RefactoringFeedback {');
     } else if (impliedType.kind == 'refactoringOptions') {
       writeln(' extends RefactoringOptions {');
+    } else if (impliedType.kind == 'requestParams') {
+      writeln(' implements RequestParams {');
     } else if (impliedType.kind == 'requestResult') {
       writeln(' implements ResponseResult {');
     } else {