Move CancelableTaskTracker to //base/task/CancelableTaskTracker.

Move CancelableTaskTracker to //base/task/CancelableTaskTracker.

CancelableTaskTracker is used by //chrome code that is due to componentized.
This CL moves the class to //base/task and wraps it in the ::base::task namespace.

BUG=335135
TBR=thakis

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=249397

[blundell, 2014-01-28 16:23:15]

Hi Darin,

Let me know if you want me to loop someone in for reviewing the //chrome changes
(which are basically mechanical). Thanks!

[blundell, 2014-01-29 18:01:13]

Hi Will,

Could you look over the addition to //base to see if it looks OK to you given
your reservations?

Thanks,

Colin

[willchan no longer on Chromium, 2014-01-29 18:05:51]

My chromium-dev@ comments on this still stand :) I wouldn't approve this, but if
another base/OWNER wants to approve, I'm fine with that.

[blundell, 2014-02-04 08:38:10]

Brett,

Could you take a look? Based on earlier suggestions, I had moved CTT into
//base/threading and renamed it to CrossThreadCancelableTaskTracker. I just saw
that you suggested creating a //base/task directory. Do you think that would be
better than what I've done here?

Thanks,

Colin

[brettw, 2014-02-04 08:45:28]

I'm not sure it needs to be renamed "CrossThread". It's maybe a bit heavyweight
to use this on a single thread, but it doesn't seem wrong to me, and I think the
name is unwieldy.

I think you should put the file in base/task/ unless somebody chimes in the
thread tomorrow that they hate that idea.

[blundell, 2014-02-04 08:49:46]

Thanks for the response! My impression (but I'm nowhere near an expert here) is
that basically the only reason to use this class as opposed to other primitives
that we have in the codebase is for the use case where you post tasks to thread
B from thread A and then later need to cancel those tasks from thread A. Is that
incorrect?

[brettw, 2014-02-04 08:56:56]

On 2014/02/04 08:49:46, blundell wrote:
> Thanks for the response! My impression (but I'm nowhere near an expert here)
is
> that basically the only reason to use this class as opposed to other
primitives
> that we have in the codebase is for the use case where you post tasks to
thread
> B from thread A and then later need to cancel those tasks from thread A. Is
that
> incorrect?

Basically. I was thinking of a case where you want to do something in the future
on the current thread and want to cancel it, but there's no delay on the class
so that wouldn't seem to be practical.

[blundell, 2014-02-04 08:59:04]

On 2014/02/04 08:56:56, brettw wrote:
> On 2014/02/04 08:49:46, blundell wrote:
> > Thanks for the response! My impression (but I'm nowhere near an expert here)
> is
> > that basically the only reason to use this class as opposed to other
> primitives
> > that we have in the codebase is for the use case where you post tasks to
> thread
> > B from thread A and then later need to cancel those tasks from thread A. Is
> that
> > incorrect?
> 
> Basically. I was thinking of a case where you want to do something in the
future
> on the current thread and want to cancel it, but there's no delay on the class
> so that wouldn't seem to be practical.

Cool. Given that, I think Will had liked the idea of adding "CrossThread" and
putting it in //base/threading in order to make it less likely that people
randomly find this and use it when they don't actually need to use it. WDYT?

[brettw, 2014-02-05 04:07:47]

I still don't like CrossThread. It's not clear why one would even be tempted to
use it if they only have one thread.

[blundell, 2014-02-05 15:27:01]

Hi Brett,

PTAL! There's a little bit of churn caused by running "git cl format".

[blundell, 2014-02-05 15:38:54]

As discussed offline, moved to //base/task/CancelableTaskTracker*

[blundell, 2014-02-05 15:46:48]

Sorry for the confusion. I had changed back to CancelableTaskTracker but didn't
update the CL description properly.

[blundell, 2014-02-05 16:47:30]

As discussed offline, moved CTT to the ::base::task namespace.

[brettw, 2014-02-06 09:04:54]

LGTM with task subnamespace removed.

[blundell, 2014-02-06 09:16:35]

On 2014/02/06 09:04:54, brettw wrote:
> LGTM with task subnamespace removed.

Reverted to PS #4, which was identical except that CTT is in the ::base
namespace. Apologies for the misunderstanding, and thanks for the review!

[blundell, 2014-02-06 10:50:10]

TBR=thakis for //chrome changes (just updates in include paths and
"s/CancelableTaskTracker/base::CancelableTaskTracker", followed by running "git
cl format").

[blundell, 2014-02-06 10:50:18]

The CQ bit was checked by blundell@chromium.org

[commit-bot: I haz the power, 2014-02-06 10:54:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/blundell@chromium.org/137263007/110001

[commit-bot: I haz the power, 2014-02-06 13:32:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/blundell@chromium.org/137263007/110001

[commit-bot: I haz the power, 2014-02-06 13:47:17]

Change committed as 249397