[Downloads] Always call DM::StartDownload() for explicit downloads.

content/browser/download/drag_download_file.cc

Index: content/browser/download/drag_download_file.cc
diff --git a/content/browser/download/drag_download_file.cc b/content/browser/download/drag_download_file.cc
index c98282e76903b0901528bcdf57f2a7ee8d848a9c..52479b8b1ce3995c7c38927304e87fed6fd55344 100644
--- a/content/browser/download/drag_download_file.cc
+++ b/content/browser/download/drag_download_file.cc
@@ -92,12 +92,10 @@ class DragDownloadFile::DragDownloadFileUI : public DownloadItem::Observer {
   void OnDownloadStarted(DownloadItem* item,
                          DownloadInterruptReason interrupt_reason) {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-    if (!item) {
-      DCHECK_NE(DOWNLOAD_INTERRUPT_REASON_NONE, interrupt_reason);
+    if (interrupt_reason != DOWNLOAD_INTERRUPT_REASON_NONE) {
       on_completed_loop_->PostTask(FROM_HERE, base::Bind(on_completed_, false));
       return;
     }
-    DCHECK_EQ(DOWNLOAD_INTERRUPT_REASON_NONE, interrupt_reason);
     download_item_ = item;
     download_item_->AddObserver(this);
   }