[Offline Pages] Generate MHTML header in the browser process.

content/browser/download/mhtml_generation_manager.h

 // Copyright (c) 2012 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 CONTENT_BROWSER_DOWNLOAD_MHTML_GENERATION_MANAGER_H_
 #define CONTENT_BROWSER_DOWNLOAD_MHTML_GENERATION_MANAGER_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <memory>
@@ skipping 43 matching lines @@
   void OnSerializeAsMHTMLResponse(
       RenderFrameHostImpl* sender,
       int job_id,
       MhtmlSaveStatus save_status,
       const std::set<std::string>& digests_of_uris_of_serialized_resources,
       base::TimeDelta renderer_main_thread_time);
 
  private:
   friend struct base::DefaultSingletonTraits<MHTMLGenerationManager>;
   class Job;
+  struct FileCreationResult {
+    base::File file;
+    int header_size = 0;
+  };
 
   MHTMLGenerationManager();
   virtual ~MHTMLGenerationManager();
 
   // Called on the file thread to create |file|.

[carlosk, 2017/04/25 01:28:08]

Append "and write the MHTML header into it".

-  static base::File CreateFile(const base::FilePath& file_path);
+  static FileCreationResult CreateFileAndWriteHeader(
+      const base::FilePath& file_path,
+      const std::string& header);
 
   // Called on the UI thread when the file that should hold the MHTML data has
   // been created.
-  void OnFileAvailable(int job_id, base::File browser_file);
+  void OnFileAvailable(int job_id, FileCreationResult result);
 
   // Called on the UI thread when a job has been finished.
   void JobFinished(Job* job, MhtmlSaveStatus save_status);
 
   // Called on the UI thread after the file got finalized and we have its size.
   void OnFileClosed(
       int job_id,
       const std::tuple<MhtmlSaveStatus, int64_t>& save_status_size);
 
   // Creates and registers a new job.
@@ skipping 10 matching lines @@
   std::map<int, std::unique_ptr<Job>> id_to_job_;
 
   int next_job_id_;
 
   DISALLOW_COPY_AND_ASSIGN(MHTMLGenerationManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_MHTML_GENERATION_MANAGER_H_