Add pdwilliams to libgui and surfaceflinger OWNERS

Test: n/a, OWNERS updates only

Change-Id: I9fbc09fbdb8bc9c5881693f13833128075299b5e
diff --git a/services/surfaceflinger/OWNERS b/services/surfaceflinger/OWNERS
index 2ece51c..6011d0d 100644
--- a/services/surfaceflinger/OWNERS
+++ b/services/surfaceflinger/OWNERS
@@ -2,6 +2,7 @@
 alecmouri@google.com
 chaviw@google.com
 lpy@google.com
+pdwilliams@google.com
 racarr@google.com
 scroggo@google.com
-vishnun@google.com
\ No newline at end of file
+vishnun@google.com