[Extensions Bindings] Add support for custom property types

extensions/renderer/api_bindings_system.h

Index: extensions/renderer/api_bindings_system.h
diff --git a/extensions/renderer/api_bindings_system.h b/extensions/renderer/api_bindings_system.h
index a21da2e1443bda3065f43decda18feb0d197de84..c8f6e72310332847e3c523ecb802d234571d11e2 100644
--- a/extensions/renderer/api_bindings_system.h
+++ b/extensions/renderer/api_bindings_system.h
@@ -33,6 +33,11 @@ class APIBindingsSystem {
  public:
   using GetAPISchemaMethod =
       base::Callback<const base::DictionaryValue&(const std::string&)>;
+  using CustomTypeHandler =
+      base::Callback<v8::Local<v8::Object>(v8::Local<v8::Context> context,
+                                           const std::string& property_name,
+                                           APIRequestHandler* request_handler,
+                                           APITypeReferenceMap* type_refs)>;
 
   APIBindingsSystem(const binding::RunJSFunction& call_js,
                     const binding::RunJSFunctionSync& call_js_sync,
@@ -72,6 +77,12 @@ class APIBindingsSystem {
   // efficient to register multiple hooks for the same API.
   APIBindingHooks* GetHooksForAPI(const std::string& api_name);
 
+  // Registers the handler for creating a custom type with the given
+  // |type_name|, where |type_name| is the fully-qualified type (e.g.
+  // storage.StorageArea).
+  void RegisterCustomType(const std::string& type_name,
+                          const CustomTypeHandler& function);
+
  private:
   // Creates a new APIBinding for the given |api_name|.
   std::unique_ptr<APIBinding> CreateNewAPIBinding(const std::string& api_name);
@@ -80,6 +91,11 @@ class APIBindingsSystem {
   // type.
   void InitializeType(const std::string& name);
 
+  // Handles creating the type for the specified property.
+  v8::Local<v8::Object> CreateCustomType(v8::Local<v8::Context> context,
+                                         const std::string& type_name,
+                                         const std::string& property_name);
+
   // The map of cached API reference types.
   APITypeReferenceMap type_reference_map_;
 
@@ -98,6 +114,8 @@ class APIBindingsSystem {
   // performance concern?
   std::map<std::string, std::unique_ptr<APIBindingHooks>> binding_hooks_;
 
+  std::map<std::string, CustomTypeHandler> custom_types_;
+
   binding::RunJSFunction call_js_;
 
   binding::RunJSFunctionSync call_js_sync_;