[Extensions Bindings] Add a bindings/ subdirectory under renderer

extensions/renderer/bindings/api_signature.cc

 // 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.
 
-#include "extensions/renderer/api_signature.h"
+#include "extensions/renderer/bindings/api_signature.h"
 
 #include <algorithm>
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/values.h"
 #include "content/public/child/v8_value_converter.h"
-#include "extensions/renderer/api_invocation_errors.h"
-#include "extensions/renderer/argument_spec.h"
+#include "extensions/renderer/bindings/api_invocation_errors.h"
+#include "extensions/renderer/bindings/argument_spec.h"
 #include "gin/arguments.h"
 
 namespace extensions {
 
 namespace {
 
 bool HasCallback(const std::vector<std::unique_ptr<ArgumentSpec>>& signature) {
   // TODO(devlin): This is how extension APIs have always determined if a
   // function has a callback, but it seems a little silly. In the long run (once
   // signatures are generated), it probably makes sense to indicate this
@@ skipping 328 matching lines @@
     pieces.push_back(
         base::StringPrintf("%s%s %s", spec->optional() ? kOptionalPrefix : "",
                            spec->GetTypeName().c_str(), spec->name().c_str()));
   }
   expected_signature_ = base::JoinString(pieces, ", ");
 
   return expected_signature_;
 }
 
 }  // namespace extensions