Do not update surface for dummy animation as long as transition is set

Transition is not set to ready until it's executed, which could happen
a bit later after the setAppVisibility where we set up the dummy.
It is rare, but an animation pass could still slip in between, and
since the transition is not ready, it modifies the scale and show a
bad wrong frame.

bug: 27742244
Change-Id: I97fb1955e810c7c4f01dc55a28d2e4ce4f47d5eb

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

@@ -1448,7 +1448,7 @@ class WindowStateAnimator {
         // the same app again before the app's surface is destroyed or saved, the surface
         // is always ready in the whole process.) If we go ahead here, the opening app
         // will be shown with the full size before the correct animation spec arrives.
-        if (mService.mAppTransition.isReady() && isDummyAnimation() &&
+        if (mService.mAppTransition.isTransitionSet() && isDummyAnimation() &&
                 mService.mOpeningApps.contains(w.mAppToken)) {
             return;
         }