Cleaned-up unused session argument.

Change-Id: Iff9d0df5f1643c581767a41a1ba4b1d43e5b45d8
diff --git a/services/core/java/com/android/server/wm/AppWindowToken.java b/services/core/java/com/android/server/wm/AppWindowToken.java
index e914cd4..a210223 100644
--- a/services/core/java/com/android/server/wm/AppWindowToken.java
+++ b/services/core/java/com/android/server/wm/AppWindowToken.java
@@ -281,7 +281,7 @@
                 Slog.w(WindowManagerService.TAG, "removeAllWindows: removing win=" + win);
             }
 
-            service.removeWindowLocked(win.mSession, win);
+            service.removeWindowLocked(win);
         }
         allAppWindows.clear();
         windows.clear();