Align base::hash_map with C++11, part 1.

Align base::hash_map with C++11, part 1.

C++11's std::hash provides a default hash for T* that hashes by pointer value.
So does MSVC's stdext::hash_value, but not GCC's __gnu_cxx::hash (and STLPort's
std::hash). To align non-MSVC with both MSVC and the standard, provide a
default hash for pointers. This removes a lot of GCC-specific hash definitions.

Confusingly, all three provide a default hash for const char * that hashes as C
string, while not changing their equality. This CL does not change this on any
platform.

BUG=420242
Committed: https://crrev.com/254bd40b3f63b8d1e484a5c88a2255681ea54e45
Cr-Commit-Position: refs/heads/master@{#299217}

[davidben, 2014-10-06 19:16:02]

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

[davidben, 2014-10-06 19:16:03]

There wasn't much chatter on the thread I sent out, so I guess I'll publish it
for review and see what people think? Not sure what the process is here as it's
not strictly a C++11 feature.

https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/cjiUwbUhQXM

This is the other half:

https://codereview.chromium.org/623383002/

[viettrungluu, 2014-10-08 17:19:44]

viettrungluu@chromium.org changed reviewers:
+ viettrungluu@chromium.org

[viettrungluu, 2014-10-08 17:19:45]

https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
File base/containers/hash_tables.h (right):

https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
base/containers/hash_tables.h:95: BASE_HASH_NAMESPACE::hash<uintptr_t> h;
You're already inside BASE_HASH_NAMESPACE.

https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
base/containers/hash_tables.h:96: return h(reinterpret_cast<uintptr_t>(value));
So you should be able to do |return hash<uintptr_t>()(value);|.

[davidben, 2014-10-08 18:04:01]

https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
File base/containers/hash_tables.h (right):

https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
base/containers/hash_tables.h:95: BASE_HASH_NAMESPACE::hash<uintptr_t> h;
On 2014/10/08 17:19:44, viettrungluu wrote:
> You're already inside BASE_HASH_NAMESPACE.

Done.

https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
base/containers/hash_tables.h:96: return h(reinterpret_cast<uintptr_t>(value));
On 2014/10/08 17:19:45, viettrungluu wrote:
> So you should be able to do |return hash<uintptr_t>()(value);|.

Done, except the cast is still needed.

[viettrungluu, 2014-10-08 18:09:29]

On 2014/10/08 18:04:01, David Benjamin wrote:
>
https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
> File base/containers/hash_tables.h (right):
> 
>
https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
> base/containers/hash_tables.h:95: BASE_HASH_NAMESPACE::hash<uintptr_t> h;
> On 2014/10/08 17:19:44, viettrungluu wrote:
> > You're already inside BASE_HASH_NAMESPACE.
> 
> Done.
> 
>
https://codereview.chromium.org/630503002/diff/20001/base/containers/hash_tab...
> base/containers/hash_tables.h:96: return
h(reinterpret_cast<uintptr_t>(value));
> On 2014/10/08 17:19:45, viettrungluu wrote:
> > So you should be able to do |return hash<uintptr_t>()(value);|.
> 
> Done, except the cast is still needed.

Oops, that's what I meant. ;)

LGTM, but I'm not a base/ owner.

[danakj, 2014-10-08 23:47:49]

LGTM

[davidben, 2014-10-09 17:57:30]

davidben@chromium.org changed reviewers:
+ brettw@chromium.org, sievers@chromium.org, sky@chromium.org

[davidben, 2014-10-09 17:57:31]

Aaaand for OWNERS coverage.

+sky for chrome/
+sievers for gpu/ (and content/ though we both have that one now)
+brettw for tools/gn

[no sievers, 2014-10-09 18:19:46]

lgtm

[sky, 2014-10-10 02:50:48]

LGTM

[brettw, 2014-10-10 22:51:39]

GN LGTM

[davidben, 2014-10-10 22:52:07]

The CQ bit was checked by davidben@chromium.org

[commit-bot: I haz the power, 2014-10-10 22:52:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/630503002/40001

[commit-bot: I haz the power, 2014-10-10 23:00:24]

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

[commit-bot: I haz the power, 2014-10-10 23:00:25]

Try jobs failed on following builders:
  mac_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/mac_gpu_triggered...)

[davidben, 2014-10-10 23:12:20]

The CQ bit was checked by davidben@chromium.org

[commit-bot: I haz the power, 2014-10-10 23:13:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/630503002/40001

[commit-bot: I haz the power, 2014-10-11 00:14:07]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2014-10-11 00:14:52]

Patchset 3 (id:??) landed as
https://crrev.com/254bd40b3f63b8d1e484a5c88a2255681ea54e45
Cr-Commit-Position: refs/heads/master@{#299217}