Switch SchedulerClock to std::chrono::steady_clock

According to
https://en.cppreference.com/w/cpp/chrono/high_resolution_clock, we
should prefer steady_clock or system_clock, depending on our needs. We
already assert that it is_steady, and we use values of this type as if
they *are* from steady_clock.

Specifically, android::scheduler::TimePoint, used throughout
SurfaceFlinger, inherits from SchedulerClock::time_point. When computing
the earliestPresentTime, we use TimePoints (aka a subclass of
high_resolution_clock::time_point), but then we assign the result to
CompositionRefreshArgs.earliestPresentTime, which is a
steady_clock::time_point.

Make this consistent by using the recommended type throughout.

Test: m

Change-Id: I10a3ba4829a60dfc83256cb9fea3736a6c8a0f94

services/surfaceflinger/Scheduler/include/scheduler/Time.h

diff --git a/services/surfaceflinger/Scheduler/include/scheduler/Time.h b/services/surfaceflinger/Scheduler/include/scheduler/Time.h
index bd4e3c2..ba1459a 100644
--- a/services/surfaceflinger/Scheduler/include/scheduler/Time.h
+++ b/services/surfaceflinger/Scheduler/include/scheduler/Time.h
@@ -26,7 +26,7 @@
 namespace scheduler {
 
 // TODO(b/185535769): Pull Clock.h to libscheduler to reuse this.
-using SchedulerClock = std::chrono::high_resolution_clock;
+using SchedulerClock = std::chrono::steady_clock;
 static_assert(SchedulerClock::is_steady);
 
 } // namespace scheduler