SF: Setup CompositionEngine::Layer

Add a Layer class to CompositionEngine, and modify ColorLayer and
BufferLayer to create them.

Also sets up CompositionEngine::LayerFE as an interface to be
implemented by the SF Layer class.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Bug: 121291683
Change-Id: I2ed83355e81f36954b034ec60dd1a24c631f4874
diff --git a/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp b/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
index 127d729..cb08b81 100644
--- a/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/CompositionEngine.cpp
@@ -16,6 +16,7 @@
 
 #include <compositionengine/impl/CompositionEngine.h>
 #include <compositionengine/impl/Display.h>
+#include <compositionengine/impl/Layer.h>
 #include <renderengine/RenderEngine.h>
 
 #include "DisplayHardware/HWComposer.h"
@@ -38,6 +39,10 @@
     return compositionengine::impl::createDisplay(*this, std::move(args));
 }
 
+std::shared_ptr<compositionengine::Layer> CompositionEngine::createLayer(LayerCreationArgs&& args) {
+    return compositionengine::impl::createLayer(*this, std::move(args));
+}
+
 HWComposer& CompositionEngine::getHwComposer() const {
     return *mHwComposer.get();
 }