GitLab

This adds "PrimaryAccount" to the names (in preparation for supporting
secondary accounts), and also makes the SignIn/SignOut names symmetric.

TBRing trivial call site update in ukm_browsertest.cc
TBR=bcwhite

Bug: 871221
Change-Id: I136a4e91154a736d58ca67c060c66a09aed8a458
Reviewed-on: https://chromium-review.googlesource.com/1209605
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589154}