Revert "Fix in app shelf style for Assistant launcher UI"

This reverts commit dabaa28e.

Reason for revert: UX wants a different behavior
BUG: http://crbug.com/1039787

Original change's description:
> Fix in app shelf style for Assistant launcher UI
> 
> With the Assistant launcher UI and new shelf design feature turned on,
> if the Assistant is triggered in tablet mode the shelf style will be
> changed back to "home shelf".
> 
> Added an additional check in ShelfConfig for the Assistant state to
> handle this case.
> 
> Bug: 1026727
> Test: Manual Test
> Change-Id: Ie9ca0980583117e5b17d21fa9257f91f3ebe5647
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1975114
> Commit-Queue: Yue Li <updowndota@chromium.org>
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#726929}

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

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1026727
Change-Id: Iaae20490e2db0154985d692f96f09f922a7b05ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1990261Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729158}

ash/app_list/app_list_controller_impl.cc

@@ -548,9 +548,6 @@ void AppListControllerImpl::OnAppListStateChanged(AppListState new_state,
   if (!app_list_features::IsAssistantLauncherUIEnabled())
     return;
 
-  ash::ShelfConfig::Get()->SetAssistantVisible(
-      new_state == AppListState::kStateEmbeddedAssistant);
-
   UpdateLauncherContainer();
 
   // Band-aid for https://b/144056527 to update visibility after AppListState

ash/public/cpp/shelf_config.h

@@ -53,8 +53,6 @@ class ASH_EXPORT ShelfConfig : public TabletModeObserver,
   // AppListControllerObserver:
   void OnAppListVisibilityWillChange(bool shown, int64_t display_id) override;
 
-  void SetAssistantVisible(bool visible);
-
   // Size of the shelf when visible (height when the shelf is horizontal and
   // width when the shelf is vertical).
   int shelf_size() const;
@@ -191,9 +189,6 @@ class ASH_EXPORT ShelfConfig : public TabletModeObserver,
   // Whether the app list (or home launcher in tablet mode) is visible.
   bool is_app_list_visible_;
 
-  // Whether the Assistant launcher UI is visible.
-  bool is_assistant_visible_ = false;
-
   // Size of the icons within shelf buttons.
   const int shelf_button_icon_size_;
   const int shelf_button_icon_size_dense_;

ash/shelf/shelf_config.cc

@@ -122,14 +122,6 @@ void ShelfConfig::OnAppListVisibilityWillChange(bool shown,
   OnShelfConfigUpdated();
 }
 
-void ShelfConfig::SetAssistantVisible(bool visible) {
-  if (is_assistant_visible_ == visible)
-    return;
-
-  is_assistant_visible_ = visible;
-  OnShelfConfigUpdated();
-}
-
 int ShelfConfig::shelf_size() const {
   return GetShelfSize(false /*ignore_in_app_state*/);
 }
@@ -212,9 +204,8 @@ bool ShelfConfig::is_in_app() const {
   const auto* session = shell->session_controller();
   if (!session)
     return false;
-
   return session->GetSessionState() == session_manager::SessionState::ACTIVE &&
-         (!is_app_list_visible_ || is_assistant_visible_);
+         !is_app_list_visible_;
 }
 
 void ShelfConfig::UpdateIsDense() {