GitLab

- Move print string functions for Tile or TileGroup from test utils to
class member functions.
- Have GetTileGroupForTesting API internally, LogSource will read data
through this API, and then provide to logger's observer(WebUI).

Bug: 1066556
Change-Id: I7baff1cdc5b1e9d3bcebcc08f31d134a60470086
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2268886
Commit-Queue: Hesen Zhang <hesen@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Auto-Submit: Hesen Zhang <hesen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#784193}