Make File::Duplicate() const

Make File::Duplicate const

BUG=

Committed: https://crrev.com/00e2bd6bccd008dcb3f6ebdd1c7a4b0852c05315
Cr-Commit-Position: refs/heads/master@{#406665}

[Ilya Kulshin, 2016-07-19 23:09:55]

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

[commit-bot: I haz the power, 2016-07-19 23:10:29]

Dry run: 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, 2016-07-20 00:52:56]

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

[commit-bot: I haz the power, 2016-07-20 00:52:57]

Dry run: This issue passed the CQ dry run.

[Ilya Kulshin, 2016-07-20 01:00:24]

kulshin@chromium.org changed reviewers:
+ dcheng@chromium.org, dsinclair@chromium.org

[Ilya Kulshin, 2016-07-20 01:00:24]

ptal

dcheng@ - base/files/*
dsinclair@ - content/browser/tracing*

[dcheng, 2016-07-20 01:35:31]

This CL seems to have a bunch of other things too:
- changing void* to const void*
- changing File* to const File* (which doesn't seem to be affected by making
Duplicate const)
- Add a private: label: note that this isn't really needed now that our macros
use = delete.

More concretely, what's the motivation for this change?

[Ilya Kulshin, 2016-07-20 01:41:04]

On 2016/07/20 01:35:31, dcheng wrote:
> This CL seems to have a bunch of other things too:
> - changing void* to const void*
> - changing File* to const File* (which doesn't seem to be affected by making
> Duplicate const)

These were needed in order to make the SCOPED_FILE_TRACE macro compile when
inside a const function. Otherwise, it would attempt to pass the this pointer
which is const to a function taking a pointer to non-const, which doesn't work.

> - Add a private: label: note that this isn't really needed now that our macros
> use = delete.

This was noted by "git cl lint". I can remove that change.

> More concretely, what's the motivation for this change?

In another one of my CLs I found myself with a const File* that I wanted to
call Duplicate() on, and I'd like to do it without requiring a const_cast.

[dcheng, 2016-07-20 02:20:54]

lgtm

[dsinclair, 2016-07-20 13:10:01]

lgtm

[Ilya Kulshin, 2016-07-20 19:01:32]

The CQ bit was checked by kulshin@chromium.org

[Ilya Kulshin, 2016-07-20 19:01:33]

The patchset sent to the CQ was uploaded after l-g-t-m from
dsinclair@chromium.org, dcheng@chromium.org
Link to the patchset: https://codereview.chromium.org/2163063002/#ps20001
(title: "Revert unneeded 'private:' label")

[commit-bot: I haz the power, 2016-07-20 19:03:19]

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, 2016-07-20 20:57:49]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-07-20 20:59:20]

Description was changed from

==========
Make File::Duplicate const


BUG=
==========

to

==========
Make File::Duplicate const

BUG=

Committed: https://crrev.com/00e2bd6bccd008dcb3f6ebdd1c7a4b0852c05315
Cr-Commit-Position: refs/heads/master@{#406665}
==========

[commit-bot: I haz the power, 2016-07-20 20:59:21]

Patchset 2 (id:??) landed as
https://crrev.com/00e2bd6bccd008dcb3f6ebdd1c7a4b0852c05315
Cr-Commit-Position: refs/heads/master@{#406665}