views/examples: Fix the format string of size_t var in RadioButton example.
views/examples: Fix the format string of size_t var in RadioButton example.

Cast from size_t to int.

TEST=compile views_examples target, it should work without errors.
R=sky@chromium.org

Review URL: http://codereview.chromium.org/8252009

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@105584 0039d316-1c4b-4281-b951-d872f2087c98

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