Add initial prototype for the GN meta-buildsystem.

tools/gn/input_file.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/input_file.h"
+
+#include "base/file_util.h"
+
+InputFile::InputFile(const SourceFile& name)
+    : name_(name),
+      dir_(name_.GetDir()),
+      contents_loaded_(false) {
+}
+
+InputFile::~InputFile() {
+}
+
+void InputFile::SetContents(const std::string& c) {
+  contents_loaded_ = true;
+  contents_ = c;
+}
+
+bool InputFile::Load(const base::FilePath& system_path) {
+  if (file_util::ReadFileToString(system_path, &contents_)) {
+    contents_loaded_ = true;
+    return true;
+  }
+  return false;
+}
+