Support more configurability in GN toolchains

tools/gn/tool.cc

+// Copyright 2014 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.
+
+#include "tools/gn/tool.h"
+
+Tool::Tool()
+    : depsformat_(DEPS_GCC),
+      restat_(false),
+      complete_(false) {
+}
+
+Tool::~Tool() {
+}
+
+void Tool::SetComplete() {
+  DCHECK(!complete_);
+  complete_ = true;
+
+  command_.FillRequiredTypes(&substitution_bits_);
+  depfile_.FillRequiredTypes(&substitution_bits_);
+  description_.FillRequiredTypes(&substitution_bits_);
+  outputs_.FillRequiredTypes(&substitution_bits_);
+  link_output_.FillRequiredTypes(&substitution_bits_);
+  depend_output_.FillRequiredTypes(&substitution_bits_);
+  rspfile_.FillRequiredTypes(&substitution_bits_);
+  rspfile_content_.FillRequiredTypes(&substitution_bits_);
+}