Add CachingHint into SurfaceFlinger

Some system layers may need to be excluded from surfaceflinger caching
for a variety of reasons, including power or image quality
considerations. This provides a mechanism for those system layers to
never be cached on the GPU.

Bug: 259311918
Test: libcompositionengine_test
Test: run test app and inspect planner state
Change-Id: I35418ad5a41cb2546e3b27b0af290bf3c31a0180
diff --git a/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp b/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp
index c9aeb24..d740350 100644
--- a/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp
+++ b/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp
@@ -727,6 +727,7 @@
         snapshot.dimmingEnabled = requested.dimmingEnabled;
         snapshot.layerOpaqueFlagSet =
                 (requested.flags & layer_state_t::eLayerOpaque) == layer_state_t::eLayerOpaque;
+        snapshot.cachingHint = requested.cachingHint;
     }
 
     if (forceUpdate || snapshot.changes.any(RequestedLayerState::Changes::Content)) {