Added 1 liner to fix shelf background hiding on side shelf alignment.

ash/shelf/shelf_layout_manager.cc

Index: ash/shelf/shelf_layout_manager.cc
diff --git a/ash/shelf/shelf_layout_manager.cc b/ash/shelf/shelf_layout_manager.cc
index 1336dc3b3daa4a49dd2a94d07905b073b333b8e2..ae7475297d520643d263482a367fe2afd15cc5c9 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -147,6 +147,8 @@ ShelfLayoutManager::ShelfLayoutManager(ShelfWidget* shelf_widget, Shelf* shelf)
       shelf_(shelf),
       window_overlaps_shelf_(false),
       mouse_over_shelf_when_auto_hide_timer_started_(false),
+      is_fullscreen_app_list_enabled_(
+          app_list::features::IsFullscreenAppListEnabled()),
       gesture_drag_status_(GESTURE_DRAG_NONE),
       gesture_drag_amount_(0.f),
       gesture_drag_auto_hide_state_(SHELF_AUTO_HIDE_SHOWN),
@@ -432,7 +434,7 @@ void ShelfLayoutManager::OnAppListVisibilityChanged(bool shown,
     return;
 
   is_app_list_visible_ = shown;
-  if (app_list::features::IsFullscreenAppListEnabled())
+  if (is_fullscreen_app_list_enabled_)
     MaybeUpdateShelfBackground(AnimationChangeType::IMMEDIATE);
 }
 
@@ -479,8 +481,14 @@ ShelfBackgroundType ShelfLayoutManager::GetShelfBackgroundType() const {
   if (state_.session_state != session_manager::SessionState::ACTIVE)
     return SHELF_BACKGROUND_OVERLAP;
 
+  // If the app list is active and the shelf is oriented vertically, enable the
+  // shelf background.
+  if (is_app_list_visible_ && !shelf_->IsHorizontalAlignment() &&
+      is_fullscreen_app_list_enabled_)
+    return SHELF_BACKGROUND_OVERLAP;
+
   // If the app list is active, hide the shelf background to prevent overlap.
-  if (is_app_list_visible_ && app_list::features::IsFullscreenAppListEnabled())
+  if (is_app_list_visible_ && is_fullscreen_app_list_enabled_)
     return SHELF_BACKGROUND_DEFAULT;
 
   if (state_.visibility_state != SHELF_AUTO_HIDE &&