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..38671868d68f668ee4ac4a507e13bcaf76a5eb69 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -479,6 +479,12 @@ 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() &&
+      app_list::features::IsFullscreenAppListEnabled())

[James Cook, 2017/06/21 23:57:33]

IsFullscreenAppListEnabled() runs a non-trivial amount of code. I think you
should either:

* Cache the result here in a local variable, or
* Cache the value in a const member variable for this class (since it won't
change at runtime and this object is torn down between tests)

[newcomer, 2017/06/22 00:16:09]

I picked option 2 because that's what I've done elsewhere!

Done.

+    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())
     return SHELF_BACKGROUND_DEFAULT;