Make SafeBrowsingDatabase's PrefixSets only updatable by swapping a new one in.

Make SafeBrowsingDatabase's PrefixSets only updatable by swapping a new one in.

This is done by turning scoped_ptr<PrefixSet> into scoped_ptr<const PrefixSet>.

While this doesn't fully address the issue of making sure there are no
updates on other threads it does help any readers trying to prove this
for themselves.

BUG=None

Committed: https://crrev.com/2298fc812850dd04509a4cd9e67ed9243952625f
Cr-Commit-Position: refs/heads/master@{#307051}

[gab, 2014-12-03 21:48:17]

gab@chromium.org changed reviewers:
+ mattm@chromium.org

[gab, 2014-12-03 21:48:17]

Matt PTAL.

I'm trying to come up with a way to enforce auto-locking, etc. to enforce this
further by design in order to avoid concurrency issues like the one I almost
introduced in one of my recent CL (hadn't it been for your fine reviewer eye).

But, in the mean time, this is already better for readability and API clarity
IMO.

Cheers,
Gab

[gab, 2014-12-03 21:49:51]

On 2014/12/03 21:48:17, gab wrote:
> Matt PTAL.
> 
> I'm trying to come up with a way to enforce auto-locking, etc. to enforce this
> further by design in order to avoid concurrency issues like the one I almost
> introduced in one of my recent CL (hadn't it been for your fine reviewer eye).
> 
> But, in the mean time, this is already better for readability and API clarity
> IMO.
> 
> Cheers,
> Gab

Looks like this doesn't patch on trunk as it's based on
https://codereview.chromium.org/744183002/ which has close line-wise changes,
but still good for review.

[mattm, 2014-12-03 23:08:19]

https://codereview.chromium.org/781613002/diff/1/chrome/browser/safe_browsing...
File chrome/browser/safe_browsing/prefix_set.cc (right):

https://codereview.chromium.org/781613002/diff/1/chrome/browser/safe_browsing...
chrome/browser/safe_browsing/prefix_set.cc:164: return scoped_ptr<const
PrefixSet>();
can these all be changed to "return nullptr;"?

https://codereview.chromium.org/781613002/diff/1/chrome/browser/safe_browsing...
chrome/browser/safe_browsing/prefix_set.cc:261: return scoped_ptr<const
PrefixSet>(
does make_scoped_ptr work here?

[gab, 2014-12-04 20:30:20]

PTAL, thanks!
Gab

https://codereview.chromium.org/781613002/diff/1/chrome/browser/safe_browsing...
File chrome/browser/safe_browsing/prefix_set.cc (right):

https://codereview.chromium.org/781613002/diff/1/chrome/browser/safe_browsing...
chrome/browser/safe_browsing/prefix_set.cc:164: return scoped_ptr<const
PrefixSet>();
On 2014/12/03 23:08:19, mattm wrote:
> can these all be changed to "return nullptr;"?

Yep :)

https://codereview.chromium.org/781613002/diff/1/chrome/browser/safe_browsing...
chrome/browser/safe_browsing/prefix_set.cc:261: return scoped_ptr<const
PrefixSet>(
On 2014/12/03 23:08:19, mattm wrote:
> does make_scoped_ptr work here?

Surprisingly, yes :-)!

(I expected it to fail as it typically can't cast, but it looks like it can deal
with const)

[mattm, 2014-12-04 22:25:43]

lgtm

[gab, 2014-12-05 17:52:40]

The CQ bit was checked by gab@chromium.org

[commit-bot: I haz the power, 2014-12-05 17:53:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/781613002/60001

[commit-bot: I haz the power, 2014-12-05 18:43:31]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2014-12-05 18:44:26]

Patchset 4 (id:??) landed as
https://crrev.com/2298fc812850dd04509a4cd9e67ed9243952625f
Cr-Commit-Position: refs/heads/master@{#307051}