Handle null Surface in createVirtualDisplay

One can pass a null Surface to createVirtualDisplay and then set the
Surface after creation. Properly handle the isSingleBuffered check for
this case.

Bug 31219726

Change-Id: I14ebaca58912fdb4989e0ba0f4c251df31e24617

services/core/java/com/android/server/display/DisplayManagerService.java

@@ -1402,7 +1402,7 @@ public final class DisplayManagerService extends SystemService {
                 throw new IllegalArgumentException("width, height, and densityDpi must be "
                         + "greater than 0");
             }
-            if (surface.isSingleBuffered()) {
+            if (surface != null && surface.isSingleBuffered()) {
                 throw new IllegalArgumentException("Surface can't be single-buffered");
             }
 
@@ -1463,6 +1463,9 @@ public final class DisplayManagerService extends SystemService {
 
         @Override // Binder call
         public void setVirtualDisplaySurface(IVirtualDisplayCallback callback, Surface surface) {
+            if (surface != null && surface.isSingleBuffered()) {
+                throw new IllegalArgumentException("Surface can't be single-buffered");
+            }
             final long token = Binder.clearCallingIdentity();
             try {
                 setVirtualDisplaySurfaceInternal(callback.asBinder(), surface);