Switched Task to use WindowContainer

Bug: 30060889
Test: Manual testing and existing tests still pass.
Change-Id: Ia56767e47ad3df400e3aa2650f6386cca14659a7
diff --git a/services/core/java/com/android/server/wm/AppWindowToken.java b/services/core/java/com/android/server/wm/AppWindowToken.java
index bfa02bb..12872dc 100644
--- a/services/core/java/com/android/server/wm/AppWindowToken.java
+++ b/services/core/java/com/android/server/wm/AppWindowToken.java
@@ -76,6 +76,7 @@
 
     final boolean voiceInteraction;
 
+    // TODO: Use getParent instead?
     Task mTask;
     /** @see WindowContainer#fillsParent() */
     private boolean mFillsParent;
@@ -373,7 +374,8 @@
         mIsExiting = false;
         removeAllWindows();
         if (mTask != null) {
-            mTask.detachChild(this);
+            mTask.mStack.mExitingAppTokens.remove(this);
+            mTask.removeChild(this);
         }
     }