[Extensions Bindings] Add a bindings/ subdirectory under renderer

extensions/renderer/bindings/argument_spec.h

 // Copyright 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 EXTENSIONS_RENDERER_ARGUMENT_SPEC_H_
-#define EXTENSIONS_RENDERER_ARGUMENT_SPEC_H_
+#ifndef EXTENSIONS_RENDERER_BINDINGS_ARGUMENT_SPEC_H_
+#define EXTENSIONS_RENDERER_BINDINGS_ARGUMENT_SPEC_H_
 
 #include <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/optional.h"
 #include "base/strings/string_piece.h"
@@ skipping 155 matching lines @@
   // The specification for 'additional properties'. This is used when we want
   // to allow the API to pass an object with arbitrary properties. Only
   // applicable for ArgumentType::OBJECT.
   std::unique_ptr<ArgumentSpec> additional_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(ArgumentSpec);
 };
 
 }  // namespace extensions
 
-#endif  // EXTENSIONS_RENDERER_ARGUMENT_SPEC_H_
+#endif  // EXTENSIONS_RENDERER_BINDINGS_ARGUMENT_SPEC_H_