aura: Add flag to indicate if a drag session is started with touch or mouse.

chrome/browser/download/download_util.cc

Index: chrome/browser/download/download_util.cc
diff --git a/chrome/browser/download/download_util.cc b/chrome/browser/download/download_util.cc
index eae46e9575391525997cfb6dd26b35b14aa2bb2e..bae55fb3966a0dbc87e91469beea8617f6d18971 100644
--- a/chrome/browser/download/download_util.cc
+++ b/chrome/browser/download/download_util.cc
@@ -397,7 +397,8 @@ void DragDownload(const DownloadItem* download,
       data,
       root_window,
       location,
-      ui::DragDropTypes::DRAG_COPY | ui::DragDropTypes::DRAG_LINK);
+      ui::DragDropTypes::DRAG_COPY | ui::DragDropTypes::DRAG_LINK,
+      ui::DragDropTypes::DRAG_EVENT_SOURCE_MOUSE);
 #else  // We are on WIN without AURA
   // We cannot use Widget::RunShellDrag on WIN since the |view| is backed by a
   // TabContentsViewWin, not a NativeWidgetWin.