Allow custom comparators for the MRUCache

Allow custom comparators for the MRUCache

//base's MRUCache allowed specifying key and value types, like
an underlying std::map<>, but the default base::MRUCache explicitly
specialized the comparator as std::less<>. Rather than require the
caller to overload std::less<> or operator<, allow the comparator
to be specified as a templated argument.

BUG=665735
Committed: https://crrev.com/b36da9dffc6fed50a8d72d1818d5a574e6502940
Cr-Commit-Position: refs/heads/master@{#434850}

[Ryan Sleevi, 2016-11-28 23:00:24]

rsleevi@chromium.org changed reviewers:
+ dcheng@chromium.org

[Ryan Sleevi, 2016-11-28 23:00:25]

dcheng: Hopefully stupid easy

[Ryan Sleevi, 2016-11-28 23:00:30]

The CQ bit was checked by rsleevi@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-28 23:03:37]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[dcheng, 2016-11-28 23:17:39]

lgtm, though I thought that in recent years, the guidance of the C++ style guide
has changed from "don't use operator overloading" to "use it where it makes
sense, e.g. to interoperate with STL":
https://google.github.io/styleguide/cppguide.html#Operator_Overloading

[Ryan Sleevi, 2016-11-28 23:19:29]

On 2016/11/28 23:17:39, dcheng wrote:
> lgtm, though I thought that in recent years, the guidance of the C++ style
guide
> has changed from "don't use operator overloading" to "use it where it makes
> sense, e.g. to interoperate with STL":
> https://google.github.io/styleguide/cppguide.html#Operator_Overloading

Yeah, right now we've got a custom comparator for X509Certificates and hashes,
to make sure people aren't mixing security-critical comparisons vs
optimizations, which is what the motivation was. It's on the list of "warts to
fix", but given we have a mix of both in the codebase, it seemed useful to
accomodate.

[commit-bot: I haz the power, 2016-11-29 02:10:48]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-11-29 02:10:49]

Dry run: This issue passed the CQ dry run.

[Ryan Sleevi, 2016-11-29 02:12:31]

The CQ bit was checked by rsleevi@chromium.org

[commit-bot: I haz the power, 2016-11-29 02:13:27]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-29 02:56:34]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1480385551645840, "parent_rev":
"4c255f7c8897d50bf5cb48e863817bd0246355fd", "commit_rev":
"14b102b13ebef496caece8bcbf4419e5d176f592"}

[commit-bot: I haz the power, 2016-11-29 02:57:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-29 03:04:14]

Description was changed from

==========
Allow custom comparators for the MRUCache

//base's MRUCache allowed specifying key and value types, like
an underlying std::map<>, but the default base::MRUCache explicitly
specialized the comparator as std::less<>. Rather than require the
caller to overload std::less<> or operator<, allow the comparator
to be specified as a templated argument.

BUG=665735
==========

to

==========
Allow custom comparators for the MRUCache

//base's MRUCache allowed specifying key and value types, like
an underlying std::map<>, but the default base::MRUCache explicitly
specialized the comparator as std::less<>. Rather than require the
caller to overload std::less<> or operator<, allow the comparator
to be specified as a templated argument.

BUG=665735

Committed: https://crrev.com/b36da9dffc6fed50a8d72d1818d5a574e6502940
Cr-Commit-Position: refs/heads/master@{#434850}
==========

[commit-bot: I haz the power, 2016-11-29 03:04:15]

Patchset 1 (id:??) landed as
https://crrev.com/b36da9dffc6fed50a8d72d1818d5a574e6502940
Cr-Commit-Position: refs/heads/master@{#434850}