Transition safe browsing from bloom filter to prefix set.

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
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=155543

[Scott Hess - ex-Googler, 2012-08-29 21:54:34]

I broke out SafeBrowsingDatabaseTest.FilterFile separate from
PrefixSetTransition because it can stick around after the transition.  In fact,
it works fine against the bloom filter version.  I could break it out as a
separate CL, but I wasn't sure it was worthwhile.

[ramant (doing other things), 2012-08-30 17:46:06]

lgtm

[Scott Hess - ex-Googler, 2012-09-07 21:10:50]

Raman,

This kept failing win_rel, with no output.  Turns out it was crashing taking the
address of the 0 element in an empty vector.  The changes to prefix_set* fix
that, and add a test (which fails when run without the fix).

Thanks,
scott

[ramant (doing other things), 2012-09-07 22:16:39]

lgtm

[commit-bot: I haz the power, 2012-09-07 22:23:06]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/shess@chromium.org/10896048/9001

[commit-bot: I haz the power, 2012-09-08 00:54:21]

Change committed as 155543