Fix an issue where tasks moving to front would collapse the stack.

ag/18759417 introduced a new call to onTaskMovedToFront which impacted
some bubbles behavior, basically while switching bubbles the
"background" app now appears to move to the front for a moment which
causes bubbles to be collapsed. The fix is to flip the flag for
bubbles switching a bit sooner than we already do.

Test: manual - have some bubbles, visit each of them once (i.e. have
               the activity launched), then visit them all again
             => verify all the bubbles can be visited both times and
               the stack doesn't collapse.
Bug: 235781358
Change-Id: Id0674cafd92d5aeb802a0da77a679996e7041b74

libs/WindowManager/Shell/src/com/android/wm/shell/bubbles/BubbleStackView.java

@@ -2220,11 +2220,10 @@ public class BubbleStackView extends FrameLayout
     private void animateSwitchBubbles() {
         // If we're no longer expanded, this is meaningless.
         if (!mIsExpanded) {
+            mIsBubbleSwitchAnimating = false;
             return;
         }
 
-        mIsBubbleSwitchAnimating = true;
-
         // The surface contains a screenshot of the animating out bubble, so we just need to animate
         // it out (and then release the GraphicBuffer).
         PhysicsAnimator.getInstance(mAnimatingOutSurfaceContainer).cancel();
@@ -2838,6 +2837,7 @@ public class BubbleStackView extends FrameLayout
             }, 0);
 
             if (!mIsExpansionAnimating) {
+                mIsBubbleSwitchAnimating = true;
                 mSurfaceSynchronizer.syncSurfaceAndRun(() -> {
                     post(this::animateSwitchBubbles);
                 });