desks: Fix unnecessary highlight on disabled new desk button.

Test: manual
Bug: 1000191
Change-Id: Iad3e0918ae6c82e3939e0e9413d93b0f58c2eda5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1782671Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692794}

ash/wm/desks/new_desk_button.cc

@@ -168,7 +168,7 @@ void NewDeskButton::OnViewUnhighlighted() {
 }
 
 void NewDeskButton::UpdateBorderState() {
-  if (IsViewHighlighted()) {
+  if (IsViewHighlighted() && DesksController::Get()->CanCreateDesks()) {
     SetBorder(views::CreateRoundedRectBorder(
         kHighlightThicknessDp, kCornerRadius,
         GetNativeTheme()->GetSystemColor(

ash/wm/overview/overview_highlight_controller.cc

@@ -260,6 +260,7 @@ void OverviewHighlightController::OnViewDestroyingOrDisabling(
   DCHECK_GE(current_index, 0);
   deleted_index_ = base::make_optional(current_index);
   highlight_widget_.reset();
+  highlighted_view_->OnViewUnhighlighted();
   highlighted_view_ = nullptr;
 }