Add initial prototype for the GN meta-buildsystem.

tools/gn/build_settings.cc

+// Copyright (c) 2013 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/build_settings.h"
+
+#include "tools/gn/filesystem_utils.h"
+
+BuildSettings::BuildSettings()
+    : item_tree_(),
+      target_manager_(this),
+      toolchain_manager_(this) {
+}
+
+BuildSettings::~BuildSettings() {
+}
+
+void BuildSettings::SetSecondarySourcePath(const SourceDir& d) {
+  secondary_source_path_ = GetFullPath(d);
+}
+
+void BuildSettings::SetBuildDir(const SourceDir& d) {
+  build_dir_ = d;
+  build_to_source_dir_string_ = InvertDir(d);
+}
+
+base::FilePath BuildSettings::GetFullPath(const SourceFile& file) const {
+  return file.Resolve(root_path_);
+}
+
+base::FilePath BuildSettings::GetFullPath(const SourceDir& dir) const {
+  return dir.Resolve(root_path_);
+}
+
+base::FilePath BuildSettings::GetFullPathSecondary(
+    const SourceFile& file) const {
+  return file.Resolve(secondary_source_path_);
+}
+
+base::FilePath BuildSettings::GetFullPathSecondary(
+    const SourceDir& dir) const {
+  return dir.Resolve(secondary_source_path_);
+}
+