gcc 4.6 warnings cleanup
gcc 4.6 warnings cleanup

BUG=87490
TEST=sync_unit_tests


Review URL: http://codereview.chromium.org/8114033

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@103941 0039d316-1c4b-4281-b951-d872f2087c98

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