Reland of AppListController refactoring part 2: Ash's AppListShowerDelegate imlementation. (patchset #1 id:1 of https://codereview.chromium.org/1872033002/ )

Reason for revert:
Relanding - this wasn't the CL that was causing the problem

Original issue's description:
> Revert of AppListController refactoring part 2: Ash's AppListShowerDelegate imlementation. (patchset #8 id:160001 of https://codereview.chromium.org/1856943003/ )
>
> Reason for revert:
> Trying revert again now that dependent patch was reverted.
>
> Original issue's description:
> > AppListController refactoring part 2: Ash's AppListShowerDelegate imlementation.
> >
> > Part 1 of the refactoring: https://crrev.com/1830293002
> > Design doc: https://docs.google.com/document/d/1M9vqTTuprMssRXs8UIVaFjQUq3lUxSzwrWoPjPvca6Q/edit?ts=56d0e9f0#heading=h.b2znwtuxd2x2
> >
> > This CL adds ash::AppListShowerDelegate, which is the Ash implementation of
> > app_list::AppListShowerDelegate. At this point it is unused - Ash is still using
> > the old ash::AppListController class to control the app list.
> >
> > BUG=557408
> >
> > Committed: https://crrev.com/412803081c9d4f4321d267133512f45ce434fc10
> > Cr-Commit-Position: refs/heads/master@{#386123}
>
> TBR=sky@chromium.org,mgiuca@chromium.org,xiyuan@chromium.org,mfomitchev@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=557408
>
> Committed: https://crrev.com/59dd5b86f9db22cb2e4baeb4155948bf006d3b68
> Cr-Commit-Position: refs/heads/master@{#386187}

TBR=sky@chromium.org,mgiuca@chromium.org,xiyuan@chromium.org,beaudoin@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
BUG=557408

Review URL: https://codereview.chromium.org/1874043002

Cr-Commit-Position: refs/heads/master@{#386251}
8 files changed