CrOS Shelf: Make shelf config react on app list _target_ visibility changes

There are still issues in the app list visibility observer patterns,
but this is a step towards smoother animations by letting the shelf
config be aware of the new "desired" state sooner.

Bug: 1006013
Change-Id: Id90e2355f8120fcb51319189288a1956506dc8f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832634
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Reviewed-by: Matthew Mourgos <mmourgos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702096}

ash/public/cpp/shelf_config.h

@@ -53,7 +53,8 @@ class ASH_EXPORT ShelfConfig : public TabletModeObserver,
                                uint32_t changed_metrics) override;
 
   // AppListControllerObserver:
-  void OnAppListVisibilityChanged(bool shown, int64_t display_id) override;
+  void OnAppListTargetVisibilityChanged(bool shown,
+                                        int64_t display_id) override;
 
   // OverviewObserver:
   void OnOverviewModeStartingAnimationComplete(bool canceled) override;

ash/shelf/shelf_config.cc

@@ -110,7 +110,8 @@ void ShelfConfig::OnDisplayMetricsChanged(const display::Display& display,
   UpdateIsDense();
 }
 
-void ShelfConfig::OnAppListVisibilityChanged(bool shown, int64_t display_id) {
+void ShelfConfig::OnAppListTargetVisibilityChanged(bool shown,
+                                                   int64_t display_id) {
   // Let's check that the app visibility mechanism isn't mis-firing, which
   // would lead to a lot of extraneous relayout work.
   DCHECK_NE(is_app_list_visible_, shown);