Properly handle the case when a parallel download becomes non-parallel

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 1274 matching lines @@
     }
   }
 
   // Successful download start.
   DCHECK(download_file_);
   DCHECK(job_);
 
   if (state_ == RESUMING_INTERNAL)
     UpdateValidatorsOnResumption(new_create_info);
 
+  // If the download uses parallel requests, and choose not to create parallel
+  // request during resumption, clear the received_slices_ vector.
+  if (!job_->UsesParallelRequests() && !received_slices_.empty()) {
+    received_bytes_ =
+        GetMaxContiguousDataBlockSizeFromBeginning(received_slices_);
+    received_slices_.clear();
+  }
+
   TransitionTo(TARGET_PENDING_INTERNAL);
 
   job_->Start();
 }
 
 void DownloadItemImpl::StartDownload() {
   BrowserThread::PostTask(
       BrowserThread::FILE, FROM_HERE,
       base::Bind(&DownloadFile::Initialize,
                  // Safe because we control download file lifetime.
@@ skipping 951 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