Files.app: Remove the asynchronous queue from the AppWindowWrapper.

AsyncUtil.Queue cannot be used as nested. But AppWindowWrapper do this and it
will cause to race condition in the future change.
This CL stops to use the queue in the AppWindowWrapper.

BUG=293925
TEST=manually
R=mtomasz@chromium.org

Review URL: https://codereview.chromium.org/23995028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225158 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225158