Replace upower with power-supply-info

BUG=chromium-os:16640
TEST=go to "chrome://system" and check the "power supply info" entry to
see if it is reasonable.

Change-Id: I3873d0817fd707ab12727e4901e7e1f90e1190b6
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: http://gerrit.chromium.org/gerrit/4975