GitLab

Makes tests use SceneState and SceneController directly, bypassing the
MainController. Cleans up the Guts protocol accordingly.

Note that we should probably get rid of all these test helpers anyway,
but it's not a priority right now.

Bug: 1045660
Change-Id: Ia02a80ad287b915a79e19fbca070b803d5379c82
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2132139
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756219}