Use ByteStream in downloads system to decouple source and sink.

content/browser/download/download_file.h

 // Copyright (c) 2011 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_DOWNLOAD_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_
 #pragma once
 
 #include <string>
 
@@ skipping 12 matching lines @@
 // the download is 'in progress': once the download has been completed or
 // cancelled, the DownloadFile is destroyed.
 class CONTENT_EXPORT DownloadFile {
  public:
   virtual ~DownloadFile() {}
 
   // If calculate_hash is true, sha256 hash will be calculated.
   // Returns net::OK on success, or a network error code on failure.
   virtual net::Error Initialize() = 0;
 
-  // Write a new chunk of data to the file.
-  // Returns net::OK on success (all bytes written to the file),
-  // or a network error code on failure.
-  virtual net::Error AppendDataToFile(const char* data, size_t data_len) = 0;
-
   // Rename the download file.
   // Returns net::OK on success, or a network error code on failure.
   virtual net::Error Rename(const FilePath& full_path) = 0;
 
   // Detach the file so it is not deleted on destruction.
   virtual void Detach() = 0;
 
   // Abort the download and automatically close the file.
   virtual void Cancel() = 0;
 
-  // Indicate that the download has finished. No new data will be received.
-  virtual void Finish() = 0;
-
   // Informs the OS that this file came from the internet.
   virtual void AnnotateWithSourceInformation() = 0;
 
   virtual FilePath FullPath() const = 0;
   virtual bool InProgress() const = 0;
   virtual int64 BytesSoFar() const = 0;
   virtual int64 CurrentSpeed() const = 0;
 
   // Set |hash| with sha256 digest for the file.
   // Returns true if digest is successfully calculated.
   virtual bool GetHash(std::string* hash) = 0;
 
   // Returns the current (intermediate) state of the hash as a byte string.
   virtual std::string GetHashState() = 0;
 
   // Cancels the download request associated with this file.
   virtual void CancelDownloadRequest() = 0;
 
   virtual int Id() const = 0;
   virtual DownloadManager* GetDownloadManager() = 0;
   virtual const DownloadId& GlobalId() const = 0;
 
   virtual std::string DebugString() const = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_