Reduce the amount of time that the phishing classifier will block the UI thread

      per iteration, based on some performance testing.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6673008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@77841 0039d316-1c4b-4281-b951-d872f2087c98