Preparation to convert GetPrimaryAccount to return CoreAccountInfo

Change client code to work as if IdentityManager::GetPrimaryAccount
where returning a CoreAccountInfo instead of an AccountInfo. Method
will be updated in a followup CL.

This CL was uploaded by git cl split.

Bug: 926204
Change-Id: I030910542a3adad311c9d5ffa11e904004b4b712
Reviewed-on: https://chromium-review.googlesource.com/c/1470757
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631961}
2 files changed