Force HALs to explicitly enable legacy method for clearing buffer caches

Some HAL implementations can't support setLayerBuffer multiple times to
clear the per-layer buffer caches. Therefore, default this behavior to
disabled, and allow HALs to explcitily enable this behavior to obtain
the necessary memory savings.

Test: play videos with both true and false on both HIDL and AIDL
Bug: 285561686
Change-Id: I928cef25e35cfc5337db4ceb8581bf5926b4fbe3
diff --git a/services/surfaceflinger/SurfaceFlingerProperties.h b/services/surfaceflinger/SurfaceFlingerProperties.h
index 080feee..951f8f8 100644
--- a/services/surfaceflinger/SurfaceFlingerProperties.h
+++ b/services/surfaceflinger/SurfaceFlingerProperties.h
@@ -102,6 +102,8 @@
 
 bool ignore_hdr_camera_layers(bool defaultValue);
 
+bool clear_slots_with_set_layer_buffer(bool defaultValue);
+
 } // namespace sysprop
 } // namespace android
 #endif // SURFACEFLINGERPROPERTIES_H_