Add runtime dependency extraction for GN.

tools/gn/build_settings.h

 // 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_BUILD_SETTINGS_H_
 #define TOOLS_GN_BUILD_SETTINGS_H_
 
 #include <map>
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "tools/gn/args.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/source_dir.h"
 #include "tools/gn/source_file.h"
 
 class Item;
-class OutputFile;
 
 // Settings for one build, which is one toplevel output directory. There
 // may be multiple Settings objects that refer to this, one for each toolchain.
 class BuildSettings {
  public:
   typedef base::Callback<void(scoped_ptr<Item>)> ItemDefinedCallback;
   typedef base::Callback<void(const std::string&)> PrintCallback;
 
   BuildSettings();
   BuildSettings(const BuildSettings& other);
@@ skipping 75 matching lines @@
 
   ItemDefinedCallback item_defined_callback_;
   PrintCallback print_callback_;
 
   scoped_ptr<std::set<SourceFile>> exec_script_whitelist_;
 
   BuildSettings& operator=(const BuildSettings& other);  // Disallow.
 };
 
 #endif  // TOOLS_GN_BUILD_SETTINGS_H_