Add new UMA stats for parallelizable download

content/browser/download/download_browsertest.cc

Index: content/browser/download/download_browsertest.cc
diff --git a/content/browser/download/download_browsertest.cc b/content/browser/download/download_browsertest.cc
index be7caf0690fee98638ecdc568ab2766567999217..525d09ef61e97ae5ca61c7e66440bc73e1a69ae1 100644
--- a/content/browser/download/download_browsertest.cc
+++ b/content/browser/download/download_browsertest.cc
@@ -324,11 +324,12 @@ class CountingDownloadFile : public DownloadFileImpl {
   void Initialize(
       const InitializeCallback& callback,
       const CancelRequestCallback& cancel_request_callback,
-      const DownloadItem::ReceivedSlices& received_slices) override {
+      const DownloadItem::ReceivedSlices& received_slices,
+      bool is_parallelizable) override {
     DCHECK_CURRENTLY_ON(BrowserThread::FILE);
     active_files_++;
     DownloadFileImpl::Initialize(callback, cancel_request_callback,
-                                 received_slices);
+                                 received_slices, is_parallelizable);
   }
 
   static void GetNumberActiveFiles(int* result) {