[Easy signin] Update the logic for getting user device list from cryptohome

[Easy signin] Update the logic for getting user device list from cryptohome

* Add retry logic if initial loads fail (to handle the case cryptohome
service has not yet started)
* Cache the loaded results.

BUG=401634
Committed: https://crrev.com/5f2d92c54f1e5e3164922d9b6ab330fd59a271b8
Cr-Commit-Position: refs/heads/master@{#296056}

[tbarzic, 2014-09-19 23:29:48]

tbarzic@chromium.org changed reviewers:
+ xiyuan@chromium.org

[tbarzic, 2014-09-19 23:29:49]

split off from https://codereview.chromium.org/576343002/

[xiyuan, 2014-09-22 20:12:44]

lgtm

https://codereview.chromium.org/583403002/diff/60001/chrome/browser/signin/ea...
File chrome/browser/signin/easy_unlock_service_signin_chromeos.cc (right):

https://codereview.chromium.org/583403002/diff/60001/chrome/browser/signin/ea...
chrome/browser/signin/easy_unlock_service_signin_chromeos.cc:22: size_t
kMaxCryptohomeBackoffIntervalMs = 10000u;
nit: size_t -> uint32

[tbarzic, 2014-09-22 20:22:27]

https://codereview.chromium.org/583403002/diff/60001/chrome/browser/signin/ea...
File chrome/browser/signin/easy_unlock_service_signin_chromeos.cc (right):

https://codereview.chromium.org/583403002/diff/60001/chrome/browser/signin/ea...
chrome/browser/signin/easy_unlock_service_signin_chromeos.cc:22: size_t
kMaxCryptohomeBackoffIntervalMs = 10000u;
On 2014/09/22 20:12:43, xiyuan wrote:
> nit: size_t -> uint32

Done.

[tbarzic, 2014-09-22 20:22:33]

The CQ bit was checked by tbarzic@chromium.org

[commit-bot: I haz the power, 2014-09-22 20:23:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/583403002/80001

[commit-bot: I haz the power, 2014-09-22 21:34:42]

Committed patchset #5 (id:80001) as d110be33ada76a3388d309a8a31000241f18b492

[commit-bot: I haz the power, 2014-09-22 21:35:22]

Patchset 5 (id:??) landed as
https://crrev.com/5f2d92c54f1e5e3164922d9b6ab330fd59a271b8
Cr-Commit-Position: refs/heads/master@{#296056}