drm_hwcomposer: composite down to a primary plane after a timeout

DrmDisplayCompositor::SquashAll is triggered after a constant timeout in
DrmCompositorWorker::Routine. It will not be triggered more than one time
between genuine hwc_set calls. SquashAll has no effect if there are protected
layers, only one layer, or any errors. On success, SquashAll produces a new
DrmDisplayComposition that owns the layers in the planes of the active
composition and makes that the new active composition. SquashAll has no effect
on SquashState.

Change-Id: I975edb21847dcf2d93245f92a6e53a4e366c6a3b
4 files changed