Use ByteStream in downloads system to decouple source and sink.

content/content_browser.gypi

 # 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.
 
 {
   'dependencies': [
     'browser/debugger/devtools_resources.gyp:devtools_resources',
     'browser/speech/proto/speech_proto.gyp:speech_proto',
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
@@ skipping 248 matching lines @@
     'browser/dom_storage/dom_storage_context_impl.cc',
     'browser/dom_storage/dom_storage_context_impl.h',
     'browser/dom_storage/dom_storage_message_filter.cc',
     'browser/dom_storage/dom_storage_message_filter.h',
     'browser/dom_storage/session_storage_namespace_impl.cc',
     'browser/dom_storage/session_storage_namespace_impl.h',
     'browser/download/base_file.cc',
     'browser/download/base_file.h',
     'browser/download/byte_stream.cc',
     'browser/download/byte_stream.h',
-    'browser/download/download_buffer.cc',
-    'browser/download/download_buffer.h',
     'browser/download/download_create_info.cc',
     'browser/download/download_create_info.h',
     'browser/download/download_file.h',
     'browser/download/download_file_impl.cc',
     'browser/download/download_file_impl.h',
     'browser/download/download_file_manager.cc',
     'browser/download/download_file_manager.h',
     'browser/download/download_item_impl.cc',
     'browser/download/download_item_impl.h',
     'browser/download/download_manager_impl.cc',
@@ skipping 681 matching lines @@
       ],
     }],
     ['input_speech==0', {
       'sources/': [
         ['exclude', '^browser/speech/'],
       ],
     }],
   ],
 }