Transition safe browsing from bloom filter to prefix set.

If there is a saved prefix set file, use it and delete the bloom
filter.  Otherwise if there is a bloom filter file, use it until first
update.  On update, construct and write a prefix set file, and delete
the bloom filter.

BUG=71832


Review URL: https://chromiumcodereview.appspot.com/10896048

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@155543 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed