SF: Split FE and CE

Make LayerFE a standalone class with no links back to Layer. Pass
LayerSnapshot from Layer into LayerFE before CompositionEngine::present
and back after.

Bug: 238781169
Test: go/wm-smoke
Test: presubmit

Change-Id: I5395fb717a931f88e2bf26395acd21e8b308961e
diff --git a/services/surfaceflinger/SurfaceFlingerFactory.h b/services/surfaceflinger/SurfaceFlingerFactory.h
index 9c4d5c8..d1f21bf 100644
--- a/services/surfaceflinger/SurfaceFlingerFactory.h
+++ b/services/surfaceflinger/SurfaceFlingerFactory.h
@@ -38,6 +38,7 @@
 class IGraphicBufferConsumer;
 class IGraphicBufferProducer;
 class Layer;
+class LayerFE;
 class StartPropertySetThread;
 class SurfaceFlinger;
 class TimeStats;
@@ -88,6 +89,7 @@
 
     virtual sp<Layer> createBufferStateLayer(const LayerCreationArgs& args) = 0;
     virtual sp<Layer> createEffectLayer(const LayerCreationArgs& args) = 0;
+    virtual sp<LayerFE> createLayerFE(const std::string& layerName) = 0;
     virtual std::unique_ptr<FrameTracer> createFrameTracer() = 0;
     virtual std::unique_ptr<frametimeline::FrameTimeline> createFrameTimeline(
             std::shared_ptr<TimeStats> timeStats, pid_t surfaceFlingerPid) = 0;