Delete unused dirtyRegion local variable

Change-Id: Ibcaf7c52ee9a80e86e51985a3af0e63bebf338fe
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 73074cb..75ba857 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -2015,7 +2015,6 @@
     ALOGV("handlePageFlip");
 
     nsecs_t latchTime = systemTime();
-    Region dirtyRegion;
 
     bool visibleRegions = false;
     const LayerVector& layers(mDrawingState.layersSortedByZ);