mac: Try to fix valgrind sanity tests 14 and 15.
mac: Try to fix valgrind sanity tests 14 and 15.

See http://code.google.com/p/chromium/issues/detail?id=96945#c4
Not the nicest patch, but it's what we get for writing tests that
explicitly rely on undefined behavior with optimizations enabled.

BUG=96945
TEST=valgrind sanity tests 14 and 15 go green on the mac memory bot

Review URL: http://codereview.chromium.org/7931012

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@101700 0039d316-1c4b-4281-b951-d872f2087c98

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