Add initial prototype for the GN meta-buildsystem.

tools/gn/input_file.h

Index: tools/gn/input_file.h
diff --git a/tools/gn/input_file.h b/tools/gn/input_file.h
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+++ b/tools/gn/input_file.h
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+// 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.
+
+#ifndef TOOLS_GN_INPUT_FILE_H_
+#define TOOLS_GN_INPUT_FILE_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "tools/gn/source_dir.h"
+#include "tools/gn/source_file.h"
+
+class InputFile {
+ public:
+  InputFile(const SourceFile& name);
+
+  // Constructor for testing. Uses an empty file path and a given contents.
+  //InputFile(const char* contents);
+  ~InputFile();
+
+  const SourceFile& name() const { return name_; }
+
+  // The directory is just a cached version of name_->GetDir() but we get this
+  // a lot so computing it once up front saves a bunch of work.
+  const SourceDir& dir() const { return dir_; }
+
+  const std::string& contents() const {
+    DCHECK(contents_loaded_);
+    return contents_;
+  }
+
+  // For testing and in cases where this input doesn't actually refer to
+  // "a file".
+  void SetContents(const std::string& c);
+
+  // Loads the given file synchronously, returning true on success. This
+  bool Load(const base::FilePath& system_path);
+
+ private:
+  SourceFile name_;
+  SourceDir dir_;
+
+  bool contents_loaded_;
+  std::string contents_;
+
+  DISALLOW_COPY_AND_ASSIGN(InputFile);
+};
+
+#endif  // TOOLS_GN_INPUT_FILE_H_