SF: Decouple MessageQueue

Define an ICompositor interface against which MessageQueue (which ought
to be an implementation detail of Scheduler) is implemented. Change the
equivocal invalidate/refresh nomenclature to commit/composite. Schedule
sampling only after composite.

Bug: 185535769
Test: libsurfaceflinger_unittest
Change-Id: I0c18f312459bae48531449f24f7b53c104fc5812
diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index 3397118..fd09ae4 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -466,9 +466,9 @@
     return false;
 }
 
-void DisplayDevice::onInvalidate() {
+void DisplayDevice::animateRefreshRateOverlay() {
     if (mRefreshRateOverlay) {
-        mRefreshRateOverlay->onInvalidate();
+        mRefreshRateOverlay->animate();
     }
 }