Don't create parallel request until download file is initialized

content/browser/download/download_item_impl.cc

Index: content/browser/download/download_item_impl.cc
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index 1132560218034b46a8b1e4f9f82f8c51bc726877..cda8b841a34ecab3ef48c12d10752bd7f15034b5 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -1063,12 +1063,6 @@ void DownloadItemImpl::UpdateValidatorsOnResumption(
   // notified when the download transitions to the IN_PROGRESS state.
 }
 
-void DownloadItemImpl::CancelRequestWithOffset(int64_t offset) {
-  DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  if (job_)
-    job_->CancelRequestWithOffset(offset);
-}
-
 void DownloadItemImpl::NotifyRemoved() {
   for (auto& observer : observers_)
     observer.OnDownloadRemoved(this);
@@ -1324,20 +1318,10 @@ void DownloadItemImpl::Start(
 
   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.
-                 base::Unretained(download_file_.get()),
-                 base::Bind(&DownloadItemImpl::OnDownloadFileInitialized,
-                            weak_ptr_factory_.GetWeakPtr()),
-                 base::Bind(&DownloadItemImpl::CancelRequestWithOffset,
-                            weak_ptr_factory_.GetWeakPtr()),
-                 received_slices_, job_ && job_->IsParallelizable()));
+  job_->Start(download_file_.get(),
+              base::Bind(&DownloadItemImpl::OnDownloadFileInitialized,
+                         weak_ptr_factory_.GetWeakPtr()),
+              GetReceivedSlices());
 }
 
 void DownloadItemImpl::OnDownloadFileInitialized(