Re-land r406064 "[GN] Add JSON project writer".

tools/gn/desc_builder.h

Index: tools/gn/desc_builder.h
diff --git a/tools/gn/desc_builder.h b/tools/gn/desc_builder.h
new file mode 100644
index 0000000000000000000000000000000000000000..1f0c395923f07b6914a5c5d4a1680a1f75ffd8a8
--- /dev/null
+++ b/tools/gn/desc_builder.h
@@ -0,0 +1,27 @@
+// 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_DESC_BUILDER_H_
+#define TOOLS_GN_DESC_BUILDER_H_
+
+#include "base/values.h"
+#include "tools/gn/target.h"
+
+class DescBuilder {
+ public:
+  // Creates Dictionary representation for given target
+  static std::unique_ptr<base::DictionaryValue> DescriptionForTarget(
+      const Target* target,
+      const std::string& what,
+      bool all,
+      bool tree,
+      bool blame);
+
+  // Creates Dictionary representation for given config
+  static std::unique_ptr<base::DictionaryValue> DescriptionForConfig(
+      const Config* config,
+      const std::string& what);
+};
+
+#endif