Domain Reliability: Don't use error code unless request failed

Domain Reliability: Don't use error code unless request failed

I was copying the error code out of the URLRequestStatus of a monitored
request whether or not the status was FAILED; in cases where it wasn't,
the error would be something random (often QUIC_PROTOCOL_ERROR).

This change makes sure that we only copy the error code when we should,
and adds a unit test to make sure that beacons for successful requests
contain net::OK even if the error field contains something else.

BUG=356791
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271038

[Deprecated (see juliatuttle), 2014-05-15 20:48:03]

PTAL, davidben.

[mmenke, 2014-05-16 14:19:32]

On 2014/05/15 20:48:03, ttuttle wrote:
> PTAL, davidben.

I'll take over for David on this one.

LGTM.  Think the fact that the status can't be deduced from the error code is
actually a bug, though one with many causes.

[Deprecated (see juliatuttle), 2014-05-16 15:44:26]

On 2014/05/16 14:19:32, mmenke wrote:
> On 2014/05/15 20:48:03, ttuttle wrote:
> > PTAL, davidben.
> 
> I'll take over for David on this one.
> 
> LGTM.  Think the fact that the status can't be deduced from the error code is
> actually a bug, though one with many causes.

I assumed that the error field was simply not initialized until the request
officially failed, at which point it was set along with the FAILURE status.

[Deprecated (see juliatuttle), 2014-05-16 15:44:58]

The CQ bit was checked by ttuttle@chromium.org

[commit-bot: I haz the power, 2014-05-16 15:45:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ttuttle@chromium.org/284103003/1

[commit-bot: I haz the power, 2014-05-16 16:57:30]

Change committed as 271038