Add a helper method to truncate SourceStream's length

content/browser/download/download_item_impl.cc

 // 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.
 
 // File method ordering: Methods in this file are in the same order as
 // in download_item_impl.h, with the following exception: The public
 // interface Start is placed in chronological order with the other
 // (private) routines that together define a DownloadItem's state
 // transitions as the download progresses.  See "Download progression
 // cascade" later in this file.
@@ skipping 1962 matching lines @@
   // request will not be dropped if the WebContents (and by extension, the
   // associated renderer) goes away before a response is received.
   std::unique_ptr<DownloadUrlParameters> download_params(
       new DownloadUrlParameters(GetURL(),
                                 storage_partition->GetURLRequestContext()));
   download_params->set_file_path(GetFullPath());
   if (received_slices_.size() > 0) {
     std::vector<DownloadItem::ReceivedSlice> slices_to_download
         = FindSlicesToDownload(received_slices_);
     download_params->set_offset(slices_to_download[0].offset);
-    download_params->set_length(slices_to_download[0].received_bytes);
   } else {
     download_params->set_offset(GetReceivedBytes());
   }
   download_params->set_last_modified(GetLastModifiedTime());
   download_params->set_etag(GetETag());
   download_params->set_hash_of_partial_file(hash_);
   download_params->set_hash_state(std::move(hash_state_));
 
   // Note that resumed downloads disallow redirects. Hence the referrer URL
   // (which is the contents of the Referer header for the last download request)
@@ skipping 181 matching lines @@
     case RESUME_MODE_USER_CONTINUE:
       return "USER_CONTINUE";
     case RESUME_MODE_USER_RESTART:
       return "USER_RESTART";
   }
   NOTREACHED() << "Unknown resume mode " << mode;
   return "unknown";
 }
 
 }  // namespace content