aw:Delete stream for download in IO thread for android_webview.

When the download request is intercepted by the webview, we will delete
the ResourceDownloader and stream as soon as possible. But the stream is
deleted in the Download task runner and the ResourceDownloader is
deleted in the IO task runner, there will be a race that the error caused by
destroying the stream send to webview before the ResourceDownloader is destroyed.

Bug:1048335

Change-Id: Iae2a62688debee6adaa7161209dd33d6ac3b32f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2592280
Commit-Queue: HuiWang <wanghui210@huawei.com>
Reviewed-by: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837947}

components/download/internal/common/in_progress_download_manager.cc

@@ -476,7 +476,7 @@ void InProgressDownloadManager::StartDownload(
     if (delegate_ && delegate_->InterceptDownload(*info)) {
       if (cancel_request_callback)
         std::move(cancel_request_callback).Run(false);
-      GetDownloadTaskRunner()->DeleteSoon(FROM_HERE, stream.release());
+      GetIOTaskRunner()->DeleteSoon(FROM_HERE, std::move(stream));
       return;
     }
   }
@@ -534,7 +534,7 @@ void InProgressDownloadManager::StartDownloadWithItem(
       std::move(cancel_request_callback).Run(false);
     // The ByteStreamReader lives and dies on the download sequence.
     if (info->result == DOWNLOAD_INTERRUPT_REASON_NONE)
-      GetDownloadTaskRunner()->DeleteSoon(FROM_HERE, stream.release());
+      GetIOTaskRunner()->DeleteSoon(FROM_HERE, std::move(stream));
     return;
   }