Revert 232852 "Linux: add a Credentials class to handle Linux ca..."

Causing 30-50% rate failure in slave* trybots.  I'm sorry Julien. :-\

> Linux: add a Credentials class to handle Linux capabilities.
> 
> (This is a re-land of https://chromiumcodereview.appspot.com/51113009/)
> 
> BUG=312380
> TBR=jorgelo@chromium.org
> 
> Review URL: https://codereview.chromium.org/58693002

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/59073002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232927 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232927
[Password Autofill] Make better use of prefilled usernames.

If a username field is prefilled, make sure to check all possible usernames
to see if we can fill instead of only filling with the preferred username if
it matches.

BUG=309817
R=isherman@chromium.org

Review URL: https://codereview.chromium.org/56653002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232928 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232928