ChromeOS: Per-user time zone: refactor tests first.

This Cl prepares tests to support per-user timezone implementation.

BUG=622555, 699472

TBR=bauerb@chromium.org,rdevlin.cronin@chromium.org,reillyg@chromium.org

Review-Url: https://codereview.chromium.org/2907493002
Cr-Original-Commit-Position: refs/heads/master@{#476478}
Committed: https://chromium.googlesource.com/chromium/src/+/410dbeb8df3d4ab140390d7d1e603163885c8c9c
Review-Url: https://codereview.chromium.org/2907493002
Cr-Commit-Position: refs/heads/master@{#476787}
29 files changed