Add some usages for string1 and string2 to avoid "assigned
but not used" warning.

Review URL: http://codereview.chromium.org/9163003
Patch from Yury Semikhatsky <yurys@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10405 ce2b1a6d-e550-0410-aec6-3dcde31c8c00