ScopedPtrMap: Added Compare template parameter.

ScopedPtrMap: Added Compare template parameter.

Allows clients to specify a custom comparison function (as in std::map).

Also added |mapped_type| and |key_compare| typedefs in ScopedPtrMap, for
compatibility with std::map.

BUG=478594
Committed: https://crrev.com/24486e2517f5bbb84bc79aa908d81ec6eb34d676
Cr-Commit-Position: refs/heads/master@{#334549}

[Matt Giuca, 2015-06-15 04:54:25]

mgiuca@chromium.org changed reviewers:
+ danakj@chromium.org

[Matt Giuca, 2015-06-15 04:54:25]

Would you believe that while I was landing ScopedPtrMap, one of the prospective
clients (GCMClientImpl) started using the Compare template parameter to
std::map.

I also found the need to access mapped_type when porting a templated function to
use ScopedPtrMap, so adding that (note: it doesn't just reflect
Container::mapped_type, which would be ScopedPtr::element_type*; rather it
returns the mapped type of the simulated map, which is Scopedptr).

This patch generally adds a bit more compatibility with std::map.

[danakj, 2015-06-15 20:09:57]

LGTM

[Matt Giuca, 2015-06-16 01:21:38]

The CQ bit was checked by mgiuca@chromium.org

[commit-bot: I haz the power, 2015-06-16 01:23:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1179083006/1

[commit-bot: I haz the power, 2015-06-16 03:30:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-16 03:31:04]

Patchset 1 (id:??) landed as
https://crrev.com/24486e2517f5bbb84bc79aa908d81ec6eb34d676
Cr-Commit-Position: refs/heads/master@{#334549}