SF: add a new behaviour for idle timer on VRR

When idle timer times out on VRR, change the refresh rate
indicator to show "- -". The render rate doesn't cange as a result
of idleness.

Bug: 333443503
Test: manual
Flag: EXEMPT bugfix
Change-Id: Ie4f51a2a9da1a5e229b3504881117b12f1fd1b6a
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 65bfce2..e3e583b 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -704,6 +704,7 @@
                                      Fps renderRate) override;
     void onCommitNotComposited(PhysicalDisplayId pacesetterDisplayId) override
             REQUIRES(kMainThreadContext);
+    void vrrDisplayIdle(bool idle) override;
 
     // ICEPowerCallback overrides:
     void notifyCpuLoadUp() override;