Create present timestamp offset for SF

Change-Id: Ic6435cca06739f749c6041c0925ca235dcc7f51e
diff --git a/configstore/1.0/ISurfaceFlingerConfigs.hal b/configstore/1.0/ISurfaceFlingerConfigs.hal
index f9a49ce..58cb9f1 100644
--- a/configstore/1.0/ISurfaceFlingerConfigs.hal
+++ b/configstore/1.0/ISurfaceFlingerConfigs.hal
@@ -70,4 +70,10 @@
      * TARGET_HAS_HDR_DISPLAY to true in BoardConfig.mk
      */
     hasHDRDisplay() generates (OptionalBool value);
+
+    /*
+     * Specify the offset in nanoseconds to add to vsync time when timestamping
+     * present fences.
+     */
+    presentTimeOffsetFromVSyncNs() generates(OptionalInt64 value);
 };