If a download is initiated by download attribute, don't use stream viewer

content/public/android/java/src/org/chromium/content/browser/ContentViewDownloadDelegate.java

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.content.browser;
 
 /**
  * Interface to be implemented by the embedder to handle file downloads.
  */
 public interface ContentViewDownloadDelegate {
     /**
     * Notify the host application that a file should be downloaded. Replaces
     * onDownloadStart from DownloadListener.
     * @param downloadInfo Information about the requested download.
+    * @param mustDownload Whether the content must be downloded. If chrome cannot resolve a MIME
+    *                     type, clicking a link will trigger a download. mustDownload is false if
+    *                     the link has no download attribute and content-disposition is not
+    *                     attachment.
     */
-    void requestHttpGetDownload(DownloadInfo downloadInfo);
+    void requestHttpGetDownload(DownloadInfo downloadInfo, boolean mustDownload);
 
     /**
      * Notify the host application that a download is started.
      * @param filename File name of the downloaded file.
      * @param mimeType Mime of the downloaded item.
      */
     void onDownloadStarted(String filename, String mimeType);
 
     /**
      * Notify the host application that a download has an extension indicating
      * a dangerous file type.
      * @param filename File name of the downloaded file.
      * @param downloadGuid The download GUID.
      */
     void onDangerousDownload(String filename, String downloadGuid);
 
     /**
      * Called when file access has been requested to complete a download.
      * @param callbackId The callback ID used to trigger success or failure of the download.
      *
      * @see DownloadController#onRequestFileAccessResult(long, boolean)
      */
     void requestFileAccess(long callbackId);
 }