This is UI side unreadable device support.

chrome/browser/resources/file_manager/js/mock_chrome.js

 // Copyright (c) 2011 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.
 
 /**
  * Mock out the chrome.fileBrowserPrivate API for use in the harness.
  */
 chrome.fileBrowserPrivate = {
 
   /**
@@ skipping 263 matching lines @@
       NOTHING_SELECTED: 'No files selected',
       ONE_FILE_SELECTED: 'One file selected, $1',
       ONE_DIRECTORY_SELECTED: 'One directory selected',
       MANY_FILES_SELECTED: '$1 files selected, $2',
       MANY_DIRECTORIES_SELECTED: '$1 directories selected',
       MANY_ENTRIES_SELECTED: '$1 items selected, $2',
 
       CONFIRM_DELETE_ONE: 'Are you sure you want to delete "$1"?',
       CONFIRM_DELETE_SOME: 'Are you sure you want to delete $1 items?',
 
+      UNKNOWN_FILESYSTEM_WARNING:'This device cannot be opened because its' +
+          ' filesystem was not recognized.',
+      UNSUPPORTED_FILESYSTEM_WARNING: 'This device cannot be opened because' +
+          ' its filesystem is not supported.',
+      FORMATTING_WARNING: 'Formatting the removable media is going to erase' +
+          ' all data. Do you wish to continue?',
+
       ID3_ALBUM: 'Album',  // TALB
       ID3_BPM: 'BPM ',  // TBPM
       ID3_COMPOSER: 'Composer',  // TCOM
       ID3_COPYRIGHT_MESSAGE: 'Copyright message',  // TCOP
       ID3_DATE: 'Date',  // TDAT
       ID3_PLAYLIST_DELAY: 'Playlist delay',  // TDLY
       ID3_ENCODED_BY: 'Encoded by',  // TENC
       ID3_LYRICIST: 'Lyricist',  // TEXT
       ID3_FILE_TYPE: 'File type',  // TFLT
       ID3_TIME: 'Time',  // TIME
@@ skipping 37 matching lines @@
 };
 
 chrome.fileBrowserHandler = {
   onExecute: {
     listeners_: [],
     addListener: function(listener) {
       chrome.fileBrowserHandler.onExecute.listeners_.push(listener);
     }
   }
 };