[Files.app] Change sort timing during metadata fetch

Previously, sort was not started until all the metadata is fetched. When fetching took a time, the user saw unsorted list for a while. With this patch, sort is happened just after every updates. User can see sorted list every time.

BUG=327479
TEST=manually tested

Review URL: https://codereview.chromium.org/113293007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243816 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243816