- Add scopes
- Rename scopes to fit hierarchy
- Scavenge weak collections before parallel phase
- Remove semi space phase which doesn't exist anymore

Bug: chromium:738865
Change-Id: Id3b72793e764f8d3597917e45185d08675b57f5d
Reviewed-on: https://chromium-review.googlesource.com/593611Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47002}