Linux: fix default browser handling.

BUG=293277
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/25122003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225816 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225816