Revert "Do not play assistant end animation when hiding"

This reverts commit f69055b7.

Reason for revert: One or the other of this CL and https://crrev.com/c/748273 (perhaps both in combination?) broke PaletteTrayTestWithVoiceInteraction.StylusBarrelButtonActivatesHighlighter on Linux ChromiumOS Tests (dbg)(1):

https://uberchromegw.corp.google.com/i/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/31692

The connection to these voice interaction Cls seems pretty clear. I can't identify which one it is, though, so while I apologize for the trouble, I'm going to revert both to ensure that the bot turns green again.

-- Chromium Sheriff

Original change's description:
> Do not play assistant end animation when hiding
> 
> When assistant is started and triggered hiding animation, during a very
> short time window if the user lifted their finger, we would try to play
> end animation.  We should avoid doing that.
> 
> BUG=b:67496461
> TEST=build and flash locally, see animation playing normally
> 
> Change-Id: Idf52f692edd9d05b16ad48687384d291b208a42e
> Reviewed-on: https://chromium-review.googlesource.com/748268
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#513208}

TBR=xiyuan@chromium.org,xiaohuic@chromium.org

Change-Id: I13b9410f76829ec1491e9191e53519914d57f7cf
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: b:67496461
Reviewed-on: https://chromium-review.googlesource.com/749849Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513271}

ash/shelf/voice_interaction_overlay.cc

@@ -849,9 +849,8 @@ void VoiceInteractionOverlay::WaitingAnimation() {
 }
 
 void VoiceInteractionOverlay::EndAnimation() {
-  if (IsBursting() || IsHidden()) {
+  if (IsBursting()) {
     // Too late, user action already fired, we have to finish what's started.
-    // Or the widget has already been hidden, no need to play the end animation.
     return;
   }
 

ash/shelf/voice_interaction_overlay.h

@@ -33,7 +33,6 @@ class ASH_EXPORT VoiceInteractionOverlay : public views::View {
     return AnimationState::BURSTING == animation_state_;
   }
   bool IsWaiting() const { return AnimationState::WAITING == animation_state_; }
-  bool IsHidden() const { return AnimationState::HIDDEN == animation_state_; }
 
  private:
   enum class AnimationState {