Fix anchor position for popups creating new credit cards with rAc().

R=estade@chromium.org
BUG=263158
TEST=save a new card via rAc() in a popup window, the "you saved a credit card"
message should show in the top right corner of the tab with no arrow.
NOTRY=true

Review URL: https://codereview.chromium.org/26430002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227943 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227943