Remove workaround for enabling tab-focusing in Chrome OS file dialog.

BUG=127222

Review URL: https://codereview.chromium.org/24992002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225910 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225910