SF: add a sysprop to control layer caching

Bug: 158790260
Test: SF unit tests
Change-Id: I7ce6e781a480ceeeefa515cdb20bb82b618f2291
diff --git a/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt b/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt
index 0e0be09..47e14f6 100644
--- a/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt
+++ b/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt
@@ -45,6 +45,10 @@
     prop_name: "ro.surface_flinger.enable_frame_rate_override"
   }
   prop {
+    api_name: "enable_layer_caching"
+    prop_name: "ro.surface_flinger.enable_layer_caching"
+  }
+  prop {
     api_name: "enable_protected_contents"
     prop_name: "ro.surface_flinger.protected_contents"
   }