Don't create parallel request until download file is initialized

content/browser/download/parallel_download_job.h

Index: content/browser/download/parallel_download_job.h
diff --git a/content/browser/download/parallel_download_job.h b/content/browser/download/parallel_download_job.h
index 907bd5df64c96ec0e700df2aa04ddfab86ef756e..68c648f149dda17775b9625e8421a380ee0c81f2 100644
--- a/content/browser/download/parallel_download_job.h
+++ b/content/browser/download/parallel_download_job.h
@@ -30,13 +30,17 @@ class CONTENT_EXPORT ParallelDownloadJob : public DownloadJobImpl,
   ~ParallelDownloadJob() override;
 
   // DownloadJobImpl implementation.
-  void Start() override;
   void Cancel(bool user_cancel) override;
   void Pause() override;
   void Resume(bool resume_request) override;
   void CancelRequestWithOffset(int64_t offset) override;
 
  protected:
+  // DownloadJobImpl implementation.
+  void OnDownloadFileInitialized(
+      const DownloadFile::InitializeCallback& callback,
+      DownloadInterruptReason result) override;
+
   // Virtual for testing.
   virtual int GetParallelRequestCount() const;
   virtual int64_t GetMinSliceSize() const;