Add plumbing for sending stretch effect to SF

Bug: 179047472
Test: builds & boots, doesn't do anything yet
Change-Id: Ib8cccdde518f0591c2f2ee3416684442f37a1e06
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 689a302..bbbb003 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3953,6 +3953,11 @@
     if (what & layer_state_t::eAutoRefreshChanged) {
         layer->setAutoRefresh(s.autoRefresh);
     }
+    if (what & layer_state_t::eStretchChanged) {
+        if (layer->setStretchEffect(s.stretchEffect)) {
+            flags |= eTraversalNeeded;
+        }
+    }
     // This has to happen after we reparent children because when we reparent to null we remove
     // child layers from current state and remove its relative z. If the children are reparented in
     // the same transaction, then we have to make sure we reparent the children first so we do not