Remove MetricsServiceObserver in favor of MetricsProvider.

Remove MetricsServiceObserver in favor of MetricsProvider.

The only user of this interface has been folded into
NetworkMetricsProvider.

BUG=409872
Committed: https://crrev.com/bbde62b5db62e2a0902e79ebc4abee980c0bb443
Cr-Commit-Position: refs/heads/master@{#293149}

[Alexei Svitkine (slow), 2014-09-02 16:51:59]

asvitkine@chromium.org changed reviewers:
+ isherman@chromium.org

[Ilya Sherman, 2014-09-03 00:28:40]

LGTM, thanks.

https://codereview.chromium.org/532623003/diff/80001/components/metrics/metri...
File components/metrics/metrics_service.cc (right):

https://codereview.chromium.org/532623003/diff/80001/components/metrics/metri...
components/metrics/metrics_service.cc:670: DCHECK(IsSingleThreaded());
nit: Hmm, is this change needed for this CL?  I've forgotten why we have both
IsSingleThreaded() and the thread_checker_ -- can you remind me?

[Alexei Svitkine (slow), 2014-09-03 13:24:41]

https://codereview.chromium.org/532623003/diff/80001/components/metrics/metri...
File components/metrics/metrics_service.cc (right):

https://codereview.chromium.org/532623003/diff/80001/components/metrics/metri...
components/metrics/metrics_service.cc:670: DCHECK(IsSingleThreaded());
On 2014/09/03 00:28:40, Ilya Sherman wrote:
> nit: Hmm, is this change needed for this CL?  I've forgotten why we have both
> IsSingleThreaded() and the thread_checker_ -- can you remind me?

These were the only things using |thread_checker_|, so with this change only
this method was left, so I just removed it entirely.

I don't think both are necessary and I think we can probably move
IsSingleThreaded to use a ThreadChecker, but if we do that, we should change all
the code at once - which should be a separate CL.

[Alexei Svitkine (slow), 2014-09-03 13:24:45]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2014-09-03 13:25:09]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/asvitkine@chromium.org/532623003/80001

[commit-bot: I haz the power, 2014-09-03 14:47:21]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[commit-bot: I haz the power, 2014-09-03 14:51:42]

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

[commit-bot: I haz the power, 2014-09-03 14:51:43]

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

[Alexei Svitkine (slow), 2014-09-03 14:56:15]

asvitkine@chromium.org changed reviewers:
+ sky@chromium.org

[Alexei Svitkine (slow), 2014-09-03 14:56:15]

+sky for chrome/browser OWNERS

[sky, 2014-09-03 16:11:04]

LGTM

[Alexei Svitkine (slow), 2014-09-03 16:12:16]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2014-09-03 16:14:53]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/asvitkine@chromium.org/532623003/80001

[commit-bot: I haz the power, 2014-09-03 16:28:22]

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

[commit-bot: I haz the power, 2014-09-03 16:28:23]

Failed to commit the patch.

[Alexei Svitkine (slow), 2014-09-03 16:29:44]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2014-09-03 16:31:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/asvitkine@chromium.org/532623003/80001

[commit-bot: I haz the power, 2014-09-03 16:34:27]

Committed patchset #2 (id:80001) as 16dc6849265d2a70f69f4be77a999b80d42937c5

[commit-bot: I haz the power, 2014-09-10 03:26:08]

Patchset 2 (id:??) landed as
https://crrev.com/bbde62b5db62e2a0902e79ebc4abee980c0bb443
Cr-Commit-Position: refs/heads/master@{#293149}