clang-plugin: Enable RecursiveASTVisitor approach by default.

tools/clang/plugins/Options.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TOOLS_CLANG_PLUGINS_OPTIONS_H_
 #define TOOLS_CLANG_PLUGINS_OPTIONS_H_
 
 namespace chrome_checker {
 
 struct Options {
-  Options()
-      : check_base_classes(false),
-        enforce_in_pdf(false),
-        enforce_in_thirdparty_webkit(false),
-        check_enum_last_value(false),
-        with_ast_visitor(false),
-        check_templates(false) {}
-
-  bool check_base_classes;
-  bool enforce_in_pdf;
-  bool enforce_in_thirdparty_webkit;  // Use in Blink code itself
-  bool check_enum_last_value;
-  bool with_ast_visitor;
-  bool check_templates;
+  bool check_base_classes = false;
+  bool enforce_in_pdf = false;
+  bool enforce_in_thirdparty_webkit = false;  // Use in Blink code itself
+  bool check_enum_last_value = false;
+  bool check_templates = false;
   bool follow_macro_expansion = false;
+  bool check_implicit_copy_ctors = false;
 };
 
 }  // namespace chrome_checker
 
 #endif  // TOOLS_CLANG_PLUGINS_OPTIONS_H_