Fix flicker to OVERVIEW state during quick switch

Here's what was happening:
- When animating to a new task, the launcher controller ends first (when
  quick switching it likely ends immediately since we're already scaled up).
- Then we get onApplyWindowInsets(), which re-builds the launcher controller.
- Finally, the window animation ends, invalidating the handler and ending
  the new controller, which sets the state to OVERVIEW.

To fix this, never create a new controller if it has ever been started.

Bug: 133508173
Change-Id: Ibd0e18e488353df73159ffbdd9a3b335bed57d98
diff --git a/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java b/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java
index 87b7326..45f34e7 100644
--- a/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java
+++ b/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java
@@ -267,6 +267,7 @@
     private MultiStateCallback mStateCallback;
     // Used to control launcher components throughout the swipe gesture.
     private AnimatorPlaybackController mLauncherTransitionController;
+    private boolean mHasLauncherTransitionControllerStarted;
 
     private T mActivity;
     private RecentsView mRecentsView;
@@ -647,8 +648,7 @@
     }
 
     private void buildAnimationController() {
-        if (mGestureEndTarget == HOME || (mLauncherTransitionController != null
-                && mLauncherTransitionController.getAnimationPlayer().isStarted())) {
+        if (mGestureEndTarget == HOME || mHasLauncherTransitionControllerStarted) {
             // We don't want a new mLauncherTransitionController if mGestureEndTarget == HOME (it
             // has its own animation) or if we're already animating the current controller.
             return;
@@ -1122,6 +1122,7 @@
             }
             mLauncherTransitionController.getAnimationPlayer().start();
         }
+        mHasLauncherTransitionControllerStarted = true;
     }
 
     /**