Add a missing case when detecting if a toast can be added

We allow only one toast window per UID to be added at a
time. We ignore windows that run exit animation but we
should also ignore windows that should be removed after
the exit animation.

bug:31340854

Change-Id: I51c21f2c0e04341697f61e4cc107f9116254b206

services/core/java/com/android/server/wm/DisplayContent.java

@@ -697,7 +697,8 @@ class DisplayContent {
         for (int i = 0; i < windowCount; i++) {
             WindowState window = windows.get(i);
             if (window.mAttrs.type == TYPE_TOAST && window.mOwnerUid == uid
-                    && !window.mPermanentlyHidden && !window.mAnimatingExit) {
+                    && !window.mPermanentlyHidden && !window.mAnimatingExit
+                    && !window.mRemoveOnExit) {
                 return false;
             }
         }