Add new UMA stats for parallelizable download

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 bfbaaa5ad4d188540c06ac83489dc5fcd86c758f..4b1aac72b45d6f2dafcc8550f34e114532ccb76f 100644
--- a/content/browser/download/download_file.h
+++ b/content/browser/download/download_file.h
@@ -51,10 +51,10 @@ class CONTENT_EXPORT DownloadFile {
   // Upon completion, |initialize_callback| will be called on the UI
   // thread as per the comment above, passing DOWNLOAD_INTERRUPT_REASON_NONE
   // on success, or a network download interrupt reason on failure.
-  virtual void Initialize(
-      const InitializeCallback& initialize_callback,
-      const CancelRequestCallback& cancel_request_callback,
-      const DownloadItem::ReceivedSlices& received_slices) = 0;
+  virtual void Initialize(const InitializeCallback& initialize_callback,
+                          const CancelRequestCallback& cancel_request_callback,
+                          const DownloadItem::ReceivedSlices& received_slices,
+                          bool is_parallelizable) = 0;
 
   // Add a byte stream reader to write into a slice of the file, used for
   // parallel download. Called on the file thread.