[AudioPlayer] merge the recent fixes of the current audio player into the new audio player

This patch merges the following changes:
- fullPaths are not removed
- appState checks are not removed (obsolete after Apps v1)

BUG=339673
TEST=manually
R=mtomasz@chromium.org

Review URL: https://codereview.chromium.org/153743003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248980 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248980