Removed remaining use of static stack ids.

Replace by windowingMode and activityType.

Test: Existing tests pass.
Test: go/wm-smoke
Bug: 64146578
Change-Id: I2ff026de3ead1a3e7136df17c68ed37d7aae5495
diff --git a/services/tests/servicestests/src/com/android/server/wm/WindowTestsBase.java b/services/tests/servicestests/src/com/android/server/wm/WindowTestsBase.java
index 4e810f2..56a3fb0 100644
--- a/services/tests/servicestests/src/com/android/server/wm/WindowTestsBase.java
+++ b/services/tests/servicestests/src/com/android/server/wm/WindowTestsBase.java
@@ -36,8 +36,6 @@
 import android.view.IWindow;
 import android.view.WindowManager;
 
-import static android.app.ActivityManager.StackId.FIRST_DYNAMIC_STACK_ID;
-import static android.app.ActivityManager.StackId.INVALID_STACK_ID;
 import static android.app.AppOpsManager.OP_NONE;
 import static android.view.DisplayAdjustments.DEFAULT_DISPLAY_ADJUSTMENTS;
 import static android.view.WindowManager.LayoutParams.FIRST_APPLICATION_WINDOW;
@@ -70,7 +68,7 @@
     // make sure we don't collide with any existing display. If we run into no other display, the
     // added display should be treated as default. This cannot be the default display
     private static int sNextDisplayId = DEFAULT_DISPLAY + 1;
-    private static int sNextStackId = FIRST_DYNAMIC_STACK_ID;
+    static int sNextStackId = 1000;
 
     private static boolean sOneTimeSetupDone = false;
     DisplayContent mDisplayContent;