[Extension Bindings] Add JS custom hook support

extensions/renderer/api_bindings_system.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_BINDINGS_SYSTEM_H_
 #define EXTENSIONS_RENDERER_API_BINDINGS_SYSTEM_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 91 matching lines @@
 
   // A map from api_name -> APIBinding for constructed APIs. APIBindings are
   // created lazily.
   std::map<std::string, std::unique_ptr<APIBinding>> api_bindings_;
 
   // A map from api_name -> APIBindingHooks for registering custom hooks.
   // TODO(devlin): This map is pretty pointer-y. Is that going to be a
   // performance concern?
   std::map<std::string, std::unique_ptr<APIBindingHooks>> binding_hooks_;
 
+  binding::RunJSFunction call_js_;
+
   // The method to retrieve the DictionaryValue describing a given extension
   // API. Curried in for testing purposes so we can use fake APIs.
   GetAPISchemaMethod get_api_schema_;
 
   // The method to call when a new API call is triggered. Curried in for testing
   // purposes. Typically, this would send an IPC to the browser to begin the
   // function work.
   SendRequestMethod send_request_;
 
   DISALLOW_COPY_AND_ASSIGN(APIBindingsSystem);
 };
 
 }  // namespace
 
 #endif  // EXTENSIONS_RENDERER_API_BINDINGS_SYSTEM_H_