Make the third party wallpaper syncable through different devices.

chrome/browser/resources/chromeos/wallpaper_manager/js/util.js

 // Copyright (c) 2013 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.
 
 var WallpaperUtil = {
   strings: null,  // Object that contains all the flags
   syncFs: null,   // syncFileSystem handler
   webkitFs: null  // webkitFileSystem handler
 };
 
@@ skipping 59 matching lines @@
  */
 WallpaperUtil.deleteWallpaperFromSyncFS = function(wallpaperFilename) {
   var thumbnailFilename = wallpaperFilename +
                           Constants.CustomWallpaperThumbnailSuffix;
   var success = function(fs) {
     fs.root.getFile(wallpaperFilename,
                     {create: false},
                     function(fe) {
                       fe.remove(function() {}, null);
                     },
-                    WallpaperUtil.onFileSystemError);
+                    function(e) {
+                      if (e.name != 'NotFoundError')

[bshe, 2016/01/13 18:43:17]

would be good to add a command why we want to ignore NotFoundError

[xdai1, 2016/01/14 23:03:51]

Done.

+                        WallpaperUtil.onFileSystemError(e);
+                    });
     fs.root.getFile(thumbnailFilename,
                     {create: false},
                     function(fe) {
                       fe.remove(function() {}, null);
                     },
-                    WallpaperUtil.onFileSystemError);
+                    function(e) {
+                      if (e.name != 'NotFoundError')
+                        WallpaperUtil.onFileSystemError(e);
+                    });
   };
   WallpaperUtil.requestSyncFS(success);
 };
 
 /**
  * Executes callback after requesting the sync settings.
  * @param {function} callback The callback will be executed.
  */
 WallpaperUtil.enabledSyncThemesCallback = function(callback) {
   chrome.wallpaperPrivate.getSyncSetting(function(setting) {
@@ skipping 143 matching lines @@
               wallpaperFilename,
               function(thumbnailData) {
                 // TODO(ranj): Ignore 'canceledWallpaper' error.
                 if (chrome.runtime.lastError) {
                   console.error(chrome.runtime.lastError.message);
                   return;
                 }
                 WallpaperUtil.storeWallpaperToLocalFS(wallpaperFilename,
                     reader.result, Constants.WallpaperDirNameEnum.ORIGINAL);
                 WallpaperUtil.storeWallpaperToLocalFS(wallpaperFilename,
-                    reader.result, Constants.WallpaperDirNameEnum.THUMBNAIL);
+                    thumbnailData, Constants.WallpaperDirNameEnum.THUMBNAIL);

[bshe, 2016/01/08 19:56:39]

this seem to fix a different issue. do you mind land in a different CL?

[xdai1, 2016/01/08 20:17:48]

Sure! I will separate it in another CL.

                 if (onSuccess)
                   onSuccess();
               });
         };
         reader.readAsArrayBuffer(file);
       }, WallpaperUtil.onFileSystemError);
     }, function(e) {}  // fail to read file, expected due to download delay
     );
   };
   WallpaperUtil.requestSyncFS(setWallpaperFromSyncCallback);
@@ skipping 116 matching lines @@
  * Runs chrome.test.sendMessage in test environment. Does nothing if running
  * in production environment.
  *
  * @param {string} message Test message to send.
  */
 WallpaperUtil.testSendMessage = function(message) {
   var test = chrome.test || window.top.chrome.test;
   if (test)
     test.sendMessage(message);
 };