[Extensions Binding] Allow for registering custom hooks

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 52 matching lines @@
   // Responds to the request with the given |request_id|, calling the callback
   // with |response|.
   void CompleteRequest(int request_id, const base::ListValue& response);
 
   // Notifies the APIEventHandler to fire the corresponding event, notifying
   // listeners.
   void FireEventInContext(const std::string& event_name,
                           v8::Local<v8::Context> context,
                           const base::ListValue& response);
 
+  // Returns the APIBindingHooks object for the given api to allow for
+  // registering custom hooks. These must be registered *before* the
+  // binding is instantiated.
+  // TODO(devlin): It's a little weird that we don't just expose a
+  // RegisterHooks-type method. Depending on how complex the hook interface
+  // is, maybe we should rethink this. Downside would be that it's less
+  // efficient to register multiple hooks for the same API.
+  APIBindingHooks* GetHooksForAPI(const std::string& api_name);
+
  private:
   // Creates a new APIBinding for the given |api_name|.
   std::unique_ptr<APIBinding> CreateNewAPIBinding(const std::string& api_name);
 
   // Handles a call into an API, adds a pending request to the
   // |request_handler_|, and calls |send_request_|.
   void OnAPICall(const std::string& name,
                  std::unique_ptr<base::ListValue> arguments,
                  v8::Isolate* isolate,
                  v8::Local<v8::Context> context,
                  v8::Local<v8::Function> callback);
 
   // The map of cached API reference types.
   ArgumentSpec::RefMap type_reference_map_;
 
   // The request handler associated with the system.
   APIRequestHandler request_handler_;
 
   // The event handler associated with the system.
   APIEventHandler event_handler_;
 
   // 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_;
+
   // 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_