Restart in Desktop if Metro tries to start up without GPU

This doesn't yet handle the case where the GPU becomes crashy. The
user would need to close and re-open Chrome, currently. That case
seems more complicated to handle because it's only down low that
we know that, not up at the chrome:: level.

This DCHECKs in https://code.google.com/p/chromium/codesearch#chromium/src/base/win/scoped_com_initializer.h&l=55
in debug, but I believe that's an unrelated problem at HEAD. (i.e. all
restarts are doing that currently.)

R=cpu@chromium.org
BUG=308736

Review URL: https://codereview.chromium.org/54093007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232836 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232836
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/55603003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232837 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232837