Support more configurability in GN toolchains

tools/gn/output_file.cc

Index: tools/gn/output_file.cc
diff --git a/tools/gn/output_file.cc b/tools/gn/output_file.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d1fb88e8ee692951c9927856d8574c131743da1e
--- /dev/null
+++ b/tools/gn/output_file.cc
@@ -0,0 +1,39 @@
+// 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/output_file.h"
+
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/source_file.h"
+
+OutputFile::OutputFile() : value_() {
+}
+
+OutputFile::OutputFile(const base::StringPiece& str)
+    : value_(str.data(), str.size()) {
+}
+
+OutputFile::OutputFile(const BuildSettings* build_settings,
+                       const SourceFile& source_file)
+    : value_(RebaseSourceAbsolutePath(source_file.value(),
+                                      build_settings->build_dir())) {
+}
+
+OutputFile::~OutputFile() {
+}
+
+SourceFile OutputFile::AsSourceFile(const BuildSettings* build_settings) const {
+  DCHECK(!value_.empty());
+  DCHECK(value_[value_.size() - 1] != '/');
+  return SourceFile(build_settings->build_dir().value() + value_);
+}
+
+SourceDir OutputFile::AsSourceDir(const BuildSettings* build_settings) const {
+  if (!value_.empty()) {
+    // Empty means the root build dir. Otherwise, we expect it to end in a
+    // slash.
+    DCHECK(value_[value_.size() - 1] == '/');
+  }
+  return SourceDir(build_settings->build_dir().value() + value_);
+}