Add new UMA stats for parallelizable download

content/browser/download/mock_download_file.cc

Index: content/browser/download/mock_download_file.cc
diff --git a/content/browser/download/mock_download_file.cc b/content/browser/download/mock_download_file.cc
index 180ea1b9f9013592ef48f9880d46d59297660578..58edddd8651de905c22516798471e69a9a5d03a8 100644
--- a/content/browser/download/mock_download_file.cc
+++ b/content/browser/download/mock_download_file.cc
@@ -14,7 +14,8 @@ namespace {
 void SuccessRun(
     const DownloadFile::InitializeCallback& initialize_callback,
     const DownloadFile::CancelRequestCallback& cancel_request_callback,
-    const DownloadItem::ReceivedSlices& received_slices) {
+    const DownloadItem::ReceivedSlices& received_slices,
+    bool is_parallelizable) {
   initialize_callback.Run(DOWNLOAD_INTERRUPT_REASON_NONE);
 }
 
@@ -23,7 +24,7 @@ void SuccessRun(
 MockDownloadFile::MockDownloadFile() {
   // This is here because |Initialize()| is normally called right after
   // construction.
-  ON_CALL(*this, Initialize(_, _, _))
+  ON_CALL(*this, Initialize(_, _, _, _))
       .WillByDefault(::testing::Invoke(SuccessRun));
 }