Ignore non-sign-in errors in ManagedUserImportHandler.

BUG=326653

Review URL: https://codereview.chromium.org/110293002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240105 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240105
Migrate from using URLs to Entries in the Files app's audio player.

This patch converts urls as soon as possible to file entries, in the initialization stage, so later only entries are used.

TEST=Tested manually.
BUG=327592

Review URL: https://codereview.chromium.org/103003004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240106 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240106