Disable flaky PhishingClassifierTest.TestClassification on Mac OS X.

BUG=316709
TBR=jam@chromium.org

Review URL: https://codereview.chromium.org/62823003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234120 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234120