Cleanup HistoryService and HistoryBackend interface

Cleanup HistoryService and HistoryBackend interface

- fix style issues in HistoryBackend (NULL -> nullptr, git cl format)
- remove superfluous #includes and forward-declaration in history_service.h
- only pass history_dir to HistoryBackend via Init()
- remove unused member variables in HistoryService

BUG=None
TBR=zea@chromium.org

Committed: https://crrev.com/7b2039ba81fbffc936aeb6e50e0a3df2f0d9fb21
Cr-Commit-Position: refs/heads/master@{#317578}

[sdefresne, 2015-02-20 17:29:57]

sdefresne@chromium.org changed reviewers:
+ noyau@chromium.org

[sdefresne, 2015-02-20 17:29:58]

noyau: please take a look.

[noyau (Ping after 24h), 2015-02-20 18:57:31]

just one question.

https://codereview.chromium.org/934083003/diff/1/chrome/browser/history/histo...
File chrome/browser/history/history_backend.h (right):

https://codereview.chromium.org/934083003/diff/1/chrome/browser/history/histo...
chrome/browser/history/history_backend.h:824: // Init is called.
you removed the todo without removing the instance variable. expected?

[sdefresne, 2015-02-23 10:27:17]

PTAL

https://codereview.chromium.org/934083003/diff/1/chrome/browser/history/histo...
File chrome/browser/history/history_backend.h (right):

https://codereview.chromium.org/934083003/diff/1/chrome/browser/history/histo...
chrome/browser/history/history_backend.h:824: // Init is called.
On 2015/02/20 at 18:57:31, noyau wrote:
> you removed the todo without removing the instance variable. expected?

Yes, The interface of TypedUrlSyncableService is slighly different from
HistoryBackendObserver (it modifies some of the passed object) and thus it
cannot be converted to implement the interface, thus the removal of the TODO
since it is wrong.

[noyau (Ping after 24h), 2015-02-23 10:39:38]

The CQ bit was checked by noyau@chromium.org

[noyau (Ping after 24h), 2015-02-23 10:39:39]

lgtm

[commit-bot: I haz the power, 2015-02-23 10:40:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/934083003/1

[commit-bot: I haz the power, 2015-02-23 10:57:46]

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

[commit-bot: I haz the power, 2015-02-23 10:57:47]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[sdefresne, 2015-02-23 13:07:35]

sdefresne@chromium.org changed reviewers:
+ zea@chromium.org

[sdefresne, 2015-02-23 13:08:41]

TBR-ing zea@chromium.org for changes to
chrome/browser/sync/profile_sync_service_typed_url_unittest.cc since they are
just adapting code to a changed API (removing an unused parameter)

[sdefresne, 2015-02-23 13:08:46]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2015-02-23 13:09:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/934083003/1

[commit-bot: I haz the power, 2015-02-23 13:11:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-23 13:12:20]

Patchset 1 (id:??) landed as
https://crrev.com/7b2039ba81fbffc936aeb6e50e0a3df2f0d9fb21
Cr-Commit-Position: refs/heads/master@{#317578}