Fix race in DataReductionProxyService read/write.

Fix race in DataReductionProxyService read/write.

CreateNetworkDelegate is called on the IO thread, but SetDataReductionProxyService
is called on the UI thread. There is the possibility for a race to occur in
reading/writing the value of the WeakPtr; we can avoid it by passing a callback
to DataReductionProxyUsageStats (instead of the WeakPtr), since we are guaranteed
that the callback is called on the UI thread.

BUG=460876
Committed: https://crrev.com/5f46d2c4e1da91e38d197e04677e68e12a7eda77
Cr-Commit-Position: refs/heads/master@{#320822}

[jeremyim, 2015-03-16 21:47:27]

jeremyim@chromium.org changed reviewers:
+ bengr@chromium.org

[jeremyim, 2015-03-16 21:47:28]

PTAL. =)

[bengr, 2015-03-16 21:58:01]

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
File
components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.cc
(right):

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.cc:120:
service_->settings()->SetUnreachable(unreachable);
Is settings() guaranteed to be non-null? If yes, perhaps it should return a
const&.

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
File components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.h
(right):

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.h:121:
void SetUnreachable(bool unreachable);
Please add a comment that describes this function.

[jeremyim, 2015-03-16 22:31:59]

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
File
components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.cc
(right):

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.cc:120:
service_->settings()->SetUnreachable(unreachable);
On 2015/03/16 21:58:01, bengr wrote:
> Is settings() guaranteed to be non-null? If yes, perhaps it should return a
> const&.

Guaranteed to be not null. (We have a check in the DRP service constructor). Bug
467734 filed, as returning a ref is fairly involved.

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
File components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.h
(right):

https://codereview.chromium.org/1012923003/diff/1/components/data_reduction_p...
components/data_reduction_proxy/core/browser/data_reduction_proxy_io_data.h:121:
void SetUnreachable(bool unreachable);
On 2015/03/16 21:58:01, bengr wrote:
> Please add a comment that describes this function.

Done.

[bengr, 2015-03-16 22:45:49]

lgtm. Would be nice to avoid the callback, but it seems ok in this case.

[jeremyim, 2015-03-16 22:48:03]

The CQ bit was checked by jeremyim@chromium.org

[commit-bot: I haz the power, 2015-03-16 22:48:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1012923003/20001

[commit-bot: I haz the power, 2015-03-16 23:21:30]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-16 23:22:25]

Patchset 2 (id:??) landed as
https://crrev.com/5f46d2c4e1da91e38d197e04677e68e12a7eda77
Cr-Commit-Position: refs/heads/master@{#320822}