Strip out safe-browsing prefix-set checksumming code.

Stripping out the instrumentation in preparation for landing code to
transition from bloom filter to prefix set.  The histograms indicate
that virtually all of the detected problems can be explained by memory
corruption, and it's reasonable to assume that the rest are, too (just
in a form the tests didn't catch).

BUG=71832


Review URL: https://chromiumcodereview.appspot.com/10892016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@153816 0039d316-1c4b-4281-b951-d872f2087c98
4 files changed