fix an issue in SF where we could miss some updates

Change-Id: I7d350bc05d1596655baddff3deaebaba58c9bcc0
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 9e3f548..6852113 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1776,6 +1776,10 @@
                 setTransactionFlags(eTransactionNeeded|eTraversalNeeded);
                 return NO_ERROR;
             }
+            case 1006:{ // send empty update
+                signalRefresh();
+                return NO_ERROR;
+            }
             case 1008:  // toggle use of hw composer
                 n = data.readInt32();
                 mDebugDisableHWC = n ? 1 : 0;