SF: add a sysprop to control layer caching

Bug: 158790260
Test: SF unit tests
Change-Id: I7ce6e781a480ceeeefa515cdb20bb82b618f2291
diff --git a/services/surfaceflinger/sysprop/SurfaceFlingerProperties.sysprop b/services/surfaceflinger/sysprop/SurfaceFlingerProperties.sysprop
index 4d25a7a..ee5542d 100644
--- a/services/surfaceflinger/sysprop/SurfaceFlingerProperties.sysprop
+++ b/services/surfaceflinger/sysprop/SurfaceFlingerProperties.sysprop
@@ -454,3 +454,12 @@
     access: Readonly
     prop_name: "ro.surface_flinger.enable_frame_rate_override"
 }
+
+# Enables Layer Caching
+prop {
+    api_name: "enable_layer_caching"
+    type: Boolean
+    scope: Public
+    access: Readonly
+    prop_name: "ro.surface_flinger.enable_layer_caching"
+}