Downloads: replace BrowserThread::FILE with task scheduler.

content/browser/download/download_file.h

Index: content/browser/download/download_file.h
diff --git a/content/browser/download/download_file.h b/content/browser/download/download_file.h
index 4b1aac72b45d6f2dafcc8550f34e114532ccb76f..e8dca961c5f33e2aa088fa43953ead0da3847329 100644
--- a/content/browser/download/download_file.h
+++ b/content/browser/download/download_file.h
@@ -22,9 +22,9 @@ namespace content {
 
 class ByteStreamReader;
 
-// These objects live exclusively on the file thread and handle the writing
-// operations for one download. These objects live only for the duration that
-// the download is 'in progress': once the download has been completed or
+// These objects live exclusively on the download sequence and handle the
+// writing operations for one download. These objects live only for the duration
+// that the download is 'in progress': once the download has been completed or
 // cancelled, the DownloadFile is destroyed.
 class CONTENT_EXPORT DownloadFile {
  public:
@@ -43,7 +43,7 @@ class CONTENT_EXPORT DownloadFile {
       RenameCompletionCallback;
 
   // Used to drop the request, when the byte stream reader should be closed on
-  // FILE thread.
+  // download sequence.
   typedef base::Callback<void(int64_t offset)> CancelRequestCallback;
 
   virtual ~DownloadFile() {}