Fix another problem with refreshing the screen when switching to/from overlay

the previous fix was incorrect. See comment in setupHardwareComposer for
full explanations.

Change-Id: Ib24a9af000b8f95cf7319f9272d34997064ceb6d
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 72c29b4..126ca39 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -277,7 +277,7 @@
             void        handleWorkList();
             void        handleRepaint();
             void        postFramebuffer();
-            void        setupHardwareComposer(Region* dirtyInOut);
+            Region      setupHardwareComposer(const Region& dirty);
             void        composeSurfaces(const Region& dirty);
             void        repaintEverything();