Clean up uses of refreshStartTime for stats.

refreshStartTime is keeps track of frame refreshes for
stats and can be set from SurfaceFlinger. This makes
subsequent changes in refactoring
SurfaceFlinger#composite cleaner and makes tracking the
metric more consistent between changes.

The refreshStartTime field can be removed entirely from
LayerFE's CompositionResult and removed as an argument
in LayerFE#onPreComposition.

Bug: b/294936197, b/329275965
Test: presubmit
Change-Id: I97988315f8982d05aec4b2684d4f5f1826a0fefa
diff --git a/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp b/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
index d87eae3..b470208 100644
--- a/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
@@ -181,10 +181,10 @@
 
     bool needsAnotherUpdate = false;
 
-    mRefreshStartTime = systemTime(SYSTEM_TIME_MONOTONIC);
+    mRefreshStartTime = args.refreshStartTime;
 
     for (auto& layer : args.layers) {
-        if (layer->onPreComposition(mRefreshStartTime, args.updatingOutputGeometryThisFrame)) {
+        if (layer->onPreComposition(args.updatingOutputGeometryThisFrame)) {
             needsAnotherUpdate = true;
         }
     }