Init displays to null layer stack

When a display is added, initialize it to use an empty layer stack, so
if it is somehow visible it will show black. It will be assigned the
real layer stack -- along with a projection and other properties -- by
window manager soon. Normally a display remains blanked until window
manager has decided what to show on it, but for HDMI connected at boot
that isn't currently the case.

Bug: 7258935
Change-Id: Ic9bb25f7a9b8d9d3772b097ab1d6fa03bc8780a1
diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index 9466944..4fc9c6a 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -89,7 +89,7 @@
       mIsSecure(isSecure),
       mSecureLayerVisible(false),
       mScreenAcquired(false),
-      mLayerStack(0),
+      mLayerStack(NO_LAYER_STACK),
       mOrientation()
 {
     init(config);
@@ -196,13 +196,13 @@
     EGLDisplay dpy = mDisplay;
     EGLSurface surface = mSurface;
 
-#ifdef EGL_ANDROID_swap_rectangle    
+#ifdef EGL_ANDROID_swap_rectangle
     if (mFlags & SWAP_RECTANGLE) {
         const Region newDirty(dirty.intersect(bounds()));
         const Rect b(newDirty.getBounds());
         eglSetSwapRectangleANDROID(dpy, surface,
                 b.left, b.top, b.width(), b.height());
-    } 
+    }
 #endif
 
     mPageFlipCount++;