Downloads: replace BrowserThread::FILE with task scheduler.

content/browser/download/download_file_impl.h

Index: content/browser/download/download_file_impl.h
diff --git a/content/browser/download/download_file_impl.h b/content/browser/download/download_file_impl.h
index 23d6ce58d2ee87e8d153bbd926fed44dc5c42bb4..d5dd8d1ea14f4b98c27cc156114cd0e976f0a1ef 100644
--- a/content/browser/download/download_file_impl.h
+++ b/content/browser/download/download_file_impl.h
@@ -38,17 +38,16 @@ class CONTENT_EXPORT DownloadFileImpl : public DownloadFile {
   // Takes ownership of the object pointed to by |request_handle|.
   // |net_log| will be used for logging the download file's events.
   // May be constructed on any thread.  All methods besides the constructor
-  // (including destruction) must occur on the FILE thread.
+  // (including destruction) must occur on the download task runner.
   //
   // Note that the DownloadFileImpl automatically reads from the passed in
   // stream, and sends updates and status of those reads to the
   // DownloadDestinationObserver.
-  DownloadFileImpl(
-      std::unique_ptr<DownloadSaveInfo> save_info,
-      const base::FilePath& default_downloads_directory,
-      std::unique_ptr<ByteStreamReader> stream_reader,
-      const net::NetLogWithSource& net_log,
-      base::WeakPtr<DownloadDestinationObserver> observer);
+  DownloadFileImpl(std::unique_ptr<DownloadSaveInfo> save_info,
+                   const base::FilePath& default_downloads_directory,
+                   std::unique_ptr<ByteStreamReader> stream_reader,
+                   const net::NetLogWithSource& net_log,
+                   base::WeakPtr<DownloadDestinationObserver> observer);
 
   ~DownloadFileImpl() override;