[Extensions Bindings] Add lastError utilities to APIBindingJSUtil

extensions/renderer/api_request_handler.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_REQUEST_HANDLER_H_
 #define EXTENSIONS_RENDERER_API_REQUEST_HANDLER_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 56 matching lines @@
   // Responds to the request with the given |request_id|, calling the callback
   // with the given |response| arguments.
   // Invalid ids are ignored.
   void CompleteRequest(int request_id,
                        const base::ListValue& response,
                        const std::string& error);
 
   // Invalidates any requests that are associated with |context|.
   void InvalidateContext(v8::Local<v8::Context> context);
 
+  APILastError* last_error() { return &last_error_; }
+
   std::set<int> GetPendingRequestIdsForTesting() const;
 
  private:
   struct PendingRequest {
     PendingRequest(v8::Isolate* isolate,
                    v8::Local<v8::Function> callback,
                    v8::Local<v8::Context> context,
                    const std::vector<v8::Local<v8::Value>>& callback_args);
     ~PendingRequest();
     PendingRequest(PendingRequest&&);
@@ skipping 21 matching lines @@
   CallJSFunction call_js_;
 
   APILastError last_error_;
 
   DISALLOW_COPY_AND_ASSIGN(APIRequestHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_API_REQUEST_HANDLER_H_