Set-up dummy animation when setting a replacing window token

Set-up dummy animation so we can start treating windows associated
with the replacing app token like they are in transition before the
new app window is ready for us to run the real transition animation.
This allows us to make the right decisions at various call points
where an animation is expected to be running for a replacing window
but the real animation isn't set yet.

Also, removed unused field indicating if an app token is animating
a replacement window since it was always set to true and checked/set
to the same value as AppWindowToken.mWillReplaceWindow.

Bug: 25645069
Change-Id: Ie216ed5bd60fb2a15da61c7050c9344c48b1c5fb
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index 13d3ee1..0ec4b18 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -3354,11 +3354,10 @@
             // preserve the old window until the new one is drawn. This prevents having a gap
             // between the removal and addition, in which no window is visible. We also want the
             // entrance of the new window to be properly animated.
-            mWindowManager.setReplacingWindow(topActivity.appToken, true /* animate */);
+            mWindowManager.setReplacingWindow(topActivity.appToken);
         }
-        final ActivityStack stack =
-                moveTaskToStackUncheckedLocked(task, stackId, toTop, forceFocus,
-                        "moveTaskToStack:" + reason);
+        final ActivityStack stack = moveTaskToStackUncheckedLocked(
+                task, stackId, toTop, forceFocus, "moveTaskToStack:" + reason);
 
         // Make sure the task has the appropriate bounds/size for the stack it is in.
         if (stackId == FULLSCREEN_WORKSPACE_STACK_ID && task.mBounds != null) {