SF: Always create LayerHistory in Scheduler

Currently if Scheduler is created when there is
only one supported display mode, LayerHistory is
not created. This optimization assumes that the
list of supported modes is never going to change
but this is not the case for TV devices.

The typical use case is when a TV dongle or
set-top box is first connected to a display
after it boots. In this cas some devices will
first report only one display mode and later
update to the full list of supported modes.

This CL changes the behaviour to always have an instance
of LayerHistory. If there's only one display mode
recordLayerHistory() and chooseRefreshRateForContent()
are noops.

The alternative to create LayerHistory on demand is
more cumbersome because we also would need to register
all already created layers.

Bug: 188872896
Test: presubmit
Change-Id: Ia236fd4a81cc736c172220ff60762ddbc3cbb83a