[InfoBar] Enable infobars in chromium test shell

BUG=158817

TEST=apply the patch and try it out!

some urls:
maps.google.com -> Displays the geolocation infobar
(sign in in content shell since thanks to Tommy that's possible these days)
mail.google.com -> sign off -> Displays the auto login infobar.
https://apprtc.appspot.com -> Displays the WebRTC infobar

Once https://codereview.chromium.org/23464091/ makes it
http://ru.wikipedia.org -> Displays the translate infobar

R=dtrainor@chromium.org, yfriedman@chromium.org

Review URL: https://codereview.chromium.org/23672047

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227924 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227924