[GN] Add JSON project writer

tools/gn/json_project_writer.h

+// Copyright (c) 2016 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_JSON_WRITER_H_
+#define TOOLS_GN_JSON_WRITER_H_
+
+#include "tools/gn/err.h"
+#include "tools/gn/target.h"
+
+class Builder;
+class BuildSettings;
+
+class JSONProjectWriter {
+ public:
+  static bool RunAndWriteFiles(const BuildSettings* build_setting,
+                               const Builder* builder,
+                               const std::string & file_name,

[brettw, 2016/07/06 22:19:27]

Style nit: no space before &

[matt.k, 2016/07/08 00:39:08]

Done.

+                               const std::string & exec_script,
+                               const std::string & exec_script_extra_args,
+                               const std::string & dir_filter_string,
+                               bool quiet,
+                               Err* err);
+};
+
+#endif