D23098: Don't crash when X11Compositor tears down

zzag created this revision.
zzag added a reviewer: KWin.
Herald added a project: KWin.
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REVISION SUMMARY
  Compositor::stop() cannot be called from destructor of the Compositor
  class because Workspace may call Compositor::updateCompositeBlocking()
  when an instance of Deleted is removed/discarded.
  
  Another solution is to call stop() method before destroying the compositor
  object, but that's against RAII.

TEST PLAN
  KWin no longer crashes when running kwin_x11 --replace command.

REPOSITORY
  R108 KWin

BRANCH
  dont-call-pure-virtual-method

REVISION DETAIL
  https://phabricator.kde.org/D23098

AFFECTED FILES
  composite.cpp
  composite.h

To: zzag, #kwin
Cc: kwin, LeGast00n, sbergeron, jraleigh, fbampaloukas, GB_2, mkulinski, ragreen, jackyalcine, Pitel, iodelay, crozbo, bwowk, ZrenBot, ngraham, alexeymin, himcesjf, lesliezhai, ali-mohamed, hardening, romangg, jensreuterberg, abetts, sebas, apol, mart