Don't force close holding space bubble.

We originally force closed the holding space bubble because the view
hierarchy was being destroyed asynchronously which caused a crash when
views attempted to notify HoldingSpaceViewDelegate of their destruction.
That code has been transitioned to use scoped ViewObservers so this is
no longer an issue.

By allowing the holding space bubble to async close, we allow it to run
its default window animation.

Bug: 1134374
Change-Id: I2211373c7519163619f7be3988c8ddcfa7e1b8bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2449832Reviewed-by: Ahmed Mehfooz <amehfooz@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#814350}

ash/system/holding_space/holding_space_tray_bubble.cc

@@ -160,10 +160,6 @@ HoldingSpaceTrayBubble::HoldingSpaceTrayBubble(
 
 HoldingSpaceTrayBubble::~HoldingSpaceTrayBubble() {
   bubble_wrapper_->bubble_view()->ResetDelegate();
-  if (bubble_wrapper_->GetBubbleWidget() &&
-      !bubble_wrapper_->GetBubbleWidget()->IsClosed()) {
-    bubble_wrapper_->GetBubbleWidget()->CloseNow();
-  }
 }
 
 void HoldingSpaceTrayBubble::AnchorUpdated() {