[windows] Fix checkmark position for WebUI CSS checkbox input elements.
[windows] Fix checkmark position for WebUI CSS checkbox input elements.

BUG=105811
TEST=Verify checkboxes render correctly in options window with any font size selected.
Review URL: http://codereview.chromium.org/8879035

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@113885 0039d316-1c4b-4281-b951-d872f2087c98

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