[Extensions Bindings] Add lastError utilities to APIBindingJSUtil

extensions/renderer/api_bindings_system_unittest.h

 // Copyright 2017 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_UNITTEST_H_
 #define EXTENSIONS_RENDERER_API_BINDINGS_SYSTEM_UNITTEST_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 53 matching lines @@
   // |last_request_|.
   void OnAPIRequest(std::unique_ptr<APIRequestHandler::Request> request,
                     v8::Local<v8::Context> context);
 
   // Checks that |last_request_| exists and was provided with the
   // |expected_name| and |expected_arguments|.
   void ValidateLastRequest(const std::string& expected_name,
                            const std::string& expected_arguments);
 
   // Wraps the given |script source| in (function(obj) { ... }) and executes
-  // the result function, passing in |object| for an argument.
-  void CallFunctionOnObject(v8::Local<v8::Context> context,
-                            v8::Local<v8::Object> object,
-                            const std::string& script_source);
+  // the result function, passing in |object| for an argument. Returns the
+  // result of calling the function.
+  v8::Local<v8::Value> CallFunctionOnObject(v8::Local<v8::Context> context,
+                                            v8::Local<v8::Object> object,
+                                            const std::string& script_source);
 
   const APIRequestHandler::Request* last_request() const {
     return last_request_.get();
   }
   void reset_last_request() { last_request_.reset(); }
   APIBindingsSystem* bindings_system() { return bindings_system_.get(); }
 
  private:
   // The API schemas for the fake APIs.
   std::map<std::string, std::unique_ptr<base::DictionaryValue>> api_schemas_;
 
   // The APIBindingsSystem associated with the test. Safe to use across multiple
   // contexts.
   std::unique_ptr<APIBindingsSystem> bindings_system_;
 
   // The last request to be received from the APIBindingsSystem, or null if
   // there is none.
   std::unique_ptr<APIRequestHandler::Request> last_request_;
 
   DISALLOW_COPY_AND_ASSIGN(APIBindingsSystemTest);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_API_BINDINGS_SYSTEM_UNITTEST_H_