Revert 117136 - separate about page into its own page (included in chrome://chrome)

Revert 117136 - separate about page into its own page (included in chrome://chrome)

for now it's only enabled in cros, but we plan to have a version for desktop chrome as well, which is why I took it out of the chromeos namespace.

BUG=109203
TEST=manual


Review URL: http://codereview.chromium.org/9124028

TBR=estade@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=117139