[rAC, OSX] Fix field alignment.
This fixes an issue around field alignment when the dialog displays
scroll bars. Previous scroll would not only display the currently
active field, but also scroll the entire view 15 pixels to the side,
thus truncating the left edge. Since the scroll view is meant to scroll
only in y-direction, this simply forces the X coordinate to 0.
BUG=332678
R=estade@chromium.org
Review URL: https://codereview.chromium.org/
141813005
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248599 0039d316-1c4b-4281-b951-d872f2087c98