[Downloads] Rework how hashes are calculated for download files.

chrome/common/extensions/api/downloads.idl

 // Copyright (c) 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.
 
 // Use the <code>chrome.downloads</code> API to programmatically initiate,
 // monitor, manipulate, and search for downloads.
 [permissions=downloads]
 namespace downloads {
   [inline_doc] dictionary HeaderNameValuePair {
     // Name of the HTTP header.
@@ skipping 30 matching lines @@
     FILE_FAILED,
     FILE_ACCESS_DENIED,
     FILE_NO_SPACE,
     FILE_NAME_TOO_LONG,
     FILE_TOO_LARGE,
     FILE_VIRUS_INFECTED,
     FILE_TRANSIENT_ERROR,
     FILE_BLOCKED,
     FILE_SECURITY_CHECK_FAILED,
     FILE_TOO_SHORT,
+    FILE_HASH_MISMATCH,
     NETWORK_FAILED,
     NETWORK_TIMEOUT,
     NETWORK_DISCONNECTED,
     NETWORK_SERVER_DOWN,
     NETWORK_INVALID_REQUEST,
     SERVER_FAILED,
     SERVER_NO_RANGE,
     SERVER_BAD_CONTENT,
     SERVER_UNAUTHORIZED,
     SERVER_CERT_PROBLEM,
@@ skipping 482 matching lines @@
     // <code>suggestion</code> object to <code>suggest</code> wins. In order to
     // avoid confusion regarding which extension will win, users should not
     // install extensions that may conflict. If the download is initiated by
     // $(ref:download) and the target filename is known before the MIME type and
     // tentative filename have been determined, pass <code>filename</code> to
     // $(ref:download) instead.
     [maxListeners=1] static void onDeterminingFilename(
         DownloadItem downloadItem, SuggestFilenameCallback suggest);
   };
 };