Ash Tray: Disable animation for status area overflow button.

The status area collapse/expand animation is currently unspec'd, so skip the
animation for now.

TEST=manually verified with --force-status-area-collapsible flag
BUG=982511

Change-Id: Idaa95fd9a2393d668ad7d154663fc1e876c184d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1903937Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Tim Song <tengs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714696}

ash/system/tray/status_area_overflow_button_tray.cc

@@ -52,6 +52,10 @@ void StatusAreaOverflowButtonTray::IconView::ToggleState(State state) {
     slide_animation_->Show();
   else if (state == CLICK_TO_COLLAPSE)
     slide_animation_->Hide();
+
+  // TODO(tengs): Currently, the collpase/expand animation is not fully spec'd,
+  // so skip it for now.
+  slide_animation_->End();
 }
 
 void StatusAreaOverflowButtonTray::IconView::AnimationEnded(