Use ByteStream in downloads system to decouple source and sink.

net/url_request/url_request_test_job.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 NET_URL_REQUEST_URL_REQUEST_TEST_JOB_H_
 #define NET_URL_REQUEST_URL_REQUEST_TEST_JOB_H_
 #pragma once
 
 #include <string>
 
@@ skipping 86 matching lines @@
                            int buf_size,
                            int *bytes_read) OVERRIDE;
   virtual void Kill() OVERRIDE;
   virtual bool GetMimeType(std::string* mime_type) const OVERRIDE;
   virtual void GetResponseInfo(HttpResponseInfo* info) OVERRIDE;
   virtual int GetResponseCode() const OVERRIDE;
   virtual bool IsRedirectResponse(GURL* location,
                                   int* http_status_code) OVERRIDE;
 
  protected:
+  // Override to specify whether the next read done from this job will
+  // return IO pending.  This controls whether or not the WAITING state will
+  // transition back to WAITING or to DATA_AVAILABLE after an asynchronous
+  // read is processed.
+  virtual bool NextReadAsync();
+
   // This is what operation we are going to do next when this job is handled.
   // When the stage is DONE, this job will not be put on the queue.
   enum Stage { WAITING, DATA_AVAILABLE, ALL_DATA, DONE };
 
   virtual ~URLRequestTestJob();
 
   // Call to process the next opeation, usually sending a notification, and
   // advancing the stage if necessary. THIS MAY DELETE THE OBJECT.
   void ProcessNextOperation();
 
@@ skipping 21 matching lines @@
   // Holds the buffer for an asynchronous ReadRawData call
   IOBuffer* async_buf_;
   int async_buf_size_;
 
   base::WeakPtrFactory<URLRequestTestJob> weak_factory_;
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_TEST_JOB_H_