Port History::QueryMostVisitedURLs to use CancelableTaskTracker

Port History::QueryMostVisitedURLs to use CancelableTaskTracker

The callback no longer receive a HistoryService::Handle, but the client
should use the base::CancelableTaskTracker::TaskId to cancel a pending
call.

The callback receive a "const history::MostVisitedURLList*" as it is not
possible to pass a reference without adding a wrapper function. Since
there is a single client (apart from unit tests) this is the simplest
way to do it.

Merge HistoryBackend::QueryMostVisitedURLsImpl into the facade function
since they now have the same prototype.

BUG=371818
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=280530

[sdefresne, 2014-06-24 15:51:06]

Please take a look (I think you're starting to get tired of those CLs).

[sdefresne, 2014-06-25 14:29:58]

+haaawk FYI

[blundell, 2014-06-26 09:21:54]

lgtm

https://codereview.chromium.org/352623002/diff/1/chrome/browser/history/histo...
File chrome/browser/history/history_service.h (right):

https://codereview.chromium.org/352623002/diff/1/chrome/browser/history/histo...
chrome/browser/history/history_service.h:314: typedef base::Callback<void(const
history::MostVisitedURLList*)>
I think that we avoid const pointers in Chromium, although I don't know the
reasoning as to why.

[sdefresne, 2014-06-28 08:00:41]

On 2014/06/26 09:21:54, blundell wrote:
> lgtm
> 
>
https://codereview.chromium.org/352623002/diff/1/chrome/browser/history/histo...
> File chrome/browser/history/history_service.h (right):
> 
>
https://codereview.chromium.org/352623002/diff/1/chrome/browser/history/histo...
> chrome/browser/history/history_service.h:314: typedef
base::Callback<void(const
> history::MostVisitedURLList*)>
> I think that we avoid const pointers in Chromium, although I don't know the
> reasoning as to why.

I'll address this in a followup CL as I've introduced other const pointers and I
think it would be better to fix all of them in the same CL.

[sdefresne, 2014-06-28 08:06:46]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2014-06-28 08:07:37]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sdefresne@chromium.org/352623002/80001

[sdefresne, 2014-06-28 08:19:56]

The CQ bit was unchecked by sdefresne@chromium.org

[sdefresne, 2014-06-28 08:21:18]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2014-06-28 08:21:40]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sdefresne@chromium.org/352623002/100001

[commit-bot: I haz the power, 2014-06-28 20:47:35]

Change committed as 280530