ANativeWindow: add query for the concrete type.

This change adds a query to the ANativeWindow interface for getting the
concrete type of the ANativeWindow.

Bug: 4086509
Change-Id: I64aa86d72fbca3b52a98e1fc35608737781a3178
diff --git a/libs/gui/SurfaceTextureClient.cpp b/libs/gui/SurfaceTextureClient.cpp
index a40fac9..111141f 100644
--- a/libs/gui/SurfaceTextureClient.cpp
+++ b/libs/gui/SurfaceTextureClient.cpp
@@ -160,6 +160,9 @@
         // SurfaceTextureClient currently never queues frames to SurfaceFlinger.
         *value = 0;
         return NO_ERROR;
+    case NATIVE_WINDOW_CONCRETE_TYPE:
+        *value = NATIVE_WINDOW_SURFACE_TEXTURE_CLIENT;
+        return NO_ERROR;
     }
     return BAD_VALUE;
 }