This enables per-phase toolbox items, which makes the toolbar easier
to understand and use.

Change-Id: I1b44d28595c118f0ba55dd64eea54415b51b93aa
Notry: true
Bug: v8:7327
Reviewed-on: https://chromium-review.googlesource.com/c/1409435Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58813}