[Extensions Bindings] Add a bindings/ subdirectory under renderer

extensions/renderer/bindings/api_binding.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_API_BINDING_H_
-#define EXTENSIONS_RENDERER_API_BINDING_H_
+#ifndef EXTENSIONS_RENDERER_BINDINGS_API_BINDING_H_
+#define EXTENSIONS_RENDERER_BINDINGS_API_BINDING_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/supports_user_data.h"
-#include "extensions/renderer/argument_spec.h"
+#include "extensions/renderer/bindings/argument_spec.h"
 #include "v8/include/v8.h"
 
 namespace base {
 class ListValue;
 }
 
 namespace gin {
 class Arguments;
 }
 
@@ skipping 126 matching lines @@
   // unavailable are removed after object instantiation.
   v8::Eternal<v8::ObjectTemplate> object_template_;
 
   base::WeakPtrFactory<APIBinding> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(APIBinding);
 };
 
 }  // namespace extensions
 
-#endif  // EXTENSIONS_RENDERER_API_BINDING_H_
+#endif  // EXTENSIONS_RENDERER_BINDINGS_API_BINDING_H_