get rid of global regions that should be tracked per display

Change-Id: I3b871860cc29f1b2fdcc22b0c577a6eae65d9296
diff --git a/services/surfaceflinger/DisplayHardware.cpp b/services/surfaceflinger/DisplayHardware.cpp
index 4b5d8ab..7e4aa83 100644
--- a/services/surfaceflinger/DisplayHardware.cpp
+++ b/services/surfaceflinger/DisplayHardware.cpp
@@ -108,7 +108,8 @@
       mDisplayId(display),
       mNativeWindow(surface),
       mFlags(0),
-      mSecureLayerVisible(false)
+      mSecureLayerVisible(false),
+      mLayerStack(0)
 {
     init(config);
 }