Fix CryptAuthApiCallFlow resulting in an error if the server returns an empty string.

Fix CryptAuthApiCallFlow resulting in an error if the server returns an empty string.
A protocol buffer message can be serialized to the empty string.

Committed: https://crrev.com/ccef7796e0fab4bde07c17e00cfdd0ed8f7956a3
Cr-Commit-Position: refs/heads/master@{#307942}

[Tim Song, 2014-12-10 23:33:27]

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

[Ilya Sherman, 2014-12-10 23:38:29]

https://codereview.chromium.org/789353003/diff/20001/components/proximity_aut...
File components/proximity_auth/cryptauth/cryptauth_api_call_flow_unittest.cc
(right):

https://codereview.chromium.org/789353003/diff/20001/components/proximity_aut...
components/proximity_auth/cryptauth/cryptauth_api_call_flow_unittest.cc:140: }
Please add a new test to provide coverage for the "kResponseBodyError" case.

[Tim Song, 2014-12-11 00:12:56]

https://codereview.chromium.org/789353003/diff/20001/components/proximity_aut...
File components/proximity_auth/cryptauth/cryptauth_api_call_flow_unittest.cc
(right):

https://codereview.chromium.org/789353003/diff/20001/components/proximity_aut...
components/proximity_auth/cryptauth/cryptauth_api_call_flow_unittest.cc:140: }
On 2014/12/10 23:38:29, Ilya Sherman wrote:
> Please add a new test to provide coverage for the "kResponseBodyError" case.

Hmm... I'm note sure how to force this error, as the URLFetcher should be
properly configured in the callback. However, I'm hesitant to change this to a
CHECK.

[Ilya Sherman, 2014-12-11 01:17:57]

Alrighty, LGTM.  Thanks.

[Tim Song, 2014-12-11 18:16:53]

The CQ bit was checked by tengs@chromium.org

[commit-bot: I haz the power, 2014-12-11 18:17:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/789353003/20001

[commit-bot: I haz the power, 2014-12-11 19:05:36]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-12-11 19:06:28]

Patchset 2 (id:??) landed as
https://crrev.com/ccef7796e0fab4bde07c17e00cfdd0ed8f7956a3
Cr-Commit-Position: refs/heads/master@{#307942}