Set the Content-Type and Content-Length headers for BG Fetch

content/browser/background_fetch/background_fetch_test_base.cc

 // 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.
 
 #include "content/browser/background_fetch/background_fetch_test_base.h"
 
 #include <stdint.h>
 #include <memory>
 #include <utility>
 
@@ skipping 115 matching lines @@
     // Write the |response_info|'s response_text to a temporary file.
     ASSERT_TRUE(base::CreateTemporaryFileInDir(temp_directory_.GetPath(),
                                                &response_path));
 
     ASSERT_NE(-1 /* error */,
               base::WriteFile(response_path, response_info.second.c_str(),
                               response_info.second.size()));
 
     download_item->SetTargetFilePath(response_path);
     download_item->SetReceivedBytes(response_info.second.size());
+    download_item->SetMimeType("text/plain");
 
     // Notify the Job Controller about the download having been updated.
     download_item->NotifyDownloadUpdated();
   }
 
   using ResponseInfo =
       std::pair<int /* status_code */, std::string /* response_text */>;
 
   // Map of URL to the response information associated with that URL.
   std::map<GURL, ResponseInfo> registered_responses_;
@@ skipping 107 matching lines @@
   // Create a ServiceWorkerFetchRequest request with the same information.
   return ServiceWorkerFetchRequest(url, method, ServiceWorkerHeaderMap(),
                                    Referrer(), false /* is_reload */);
 }
 
 MockDownloadManager* BackgroundFetchTestBase::download_manager() {
   return download_manager_;
 }
 
 }  // namespace content