[filemanager] Set default sort to Date.

This was broken by columns rename.

BUG=chromium-os:29874
TEST=See bug.
Review URL: https://chromiumcodereview.appspot.com/10205011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133665 0039d316-1c4b-4281-b951-d872f2087c98

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

@@ -503,7 +503,8 @@ FileManager.prototype = {
     this.summarizeSelection_();
 
     var sortField =
-        window.localStorage['sort-field-' + this.dialogType_] || 'cachedMtime_';
+        window.localStorage['sort-field-' + this.dialogType_] ||
+        'modificationTime';
     var sortDirection =
         window.localStorage['sort-direction-' + this.dialogType_] || 'desc';
     this.directoryModel_.sortFileList(sortField, sortDirection);