Allow directories for GN data lists.

tools/gn/output_file.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/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(std::string&& v)
+    : value_(v) {
+}
+
+OutputFile::OutputFile(const std::string& v)
+    : value_(v) {
 }
 
 OutputFile::OutputFile(const BuildSettings* build_settings,
                        const SourceFile& source_file)
     : value_(RebasePath(source_file.value(),
                         build_settings->build_dir(),
                         build_settings->root_path_utf8())) {
 }
 
 OutputFile::~OutputFile() {
@@ skipping 13 matching lines @@
   if (!value_.empty()) {
     // Empty means the root build dir. Otherwise, we expect it to end in a
     // slash.
     DCHECK(value_[value_.size() - 1] == '/');
   }
   std::string path = build_settings->build_dir().value();
   path.append(value_);
   NormalizePath(&path);
   return SourceDir(path);
 }