Fix incorrect usage of ProfileInfoCache in GAIAInfoUpdateService.

Fix incorrect usage of ProfileInfoCache in GAIAInfoUpdateService: SetGAIANameOfProfileAtIndex may change the profile index.
Also add some warning comments in profile_info_cache.h.

BUG=372381
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282095

[Marc Treib, 2014-07-08 13:31:05]

PTAL!

[noms (inactive), 2014-07-09 14:57:55]

lgtm

[Marc Treib, 2014-07-09 15:04:18]

The CQ bit was checked by treib@chromium.org

[commit-bot: I haz the power, 2014-07-09 15:05:36]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/treib@chromium.org/373083002/1

[commit-bot: I haz the power, 2014-07-09 17:35:47]

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

[commit-bot: I haz the power, 2014-07-09 17:49:52]

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

[commit-bot: I haz the power, 2014-07-09 17:49:53]

Try jobs failed on following builders:
  ios_dbg_simulator on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/ios_dbg_simulator/bui...)

[Marc Treib, 2014-07-09 18:46:12]

The CQ bit was checked by treib@chromium.org

[commit-bot: I haz the power, 2014-07-09 18:46:49]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/treib@chromium.org/373083002/1

[commit-bot: I haz the power, 2014-07-09 19:01:40]

Change committed as 282095

[Pam (message me for reviews), 2014-07-10 22:39:14]

https://codereview.chromium.org/373083002/diff/1/chrome/browser/profiles/gaia...
File chrome/browser/profiles/gaia_info_update_service.cc (right):

https://codereview.chromium.org/373083002/diff/1/chrome/browser/profiles/gaia...
chrome/browser/profiles/gaia_info_update_service.cc:126: profile_index =
cache.GetIndexOfProfileWithPath(profile_->GetPath());

Good catch -- please add a test for the bug.