Split Shell::ToggleAppList() into ShowAppList and DismissAppList.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 14e1f9144cdffef725d80b85ce2509ac741efe46..c8d0a9a11a1e827be3ed8843b12da54afd8f8d30 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -231,10 +231,13 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   void ShowContextMenu(const gfx::Point& location_in_screen,
                        ui::MenuSourceType source_type);
 
-  // Toggles the app list. |window| specifies in which display the app
+  // Shows the app list. |window| specifies in which display the app
   // list should be shown. If this is NULL, the active root window
   // will be used.
-  void ToggleAppList(aura::Window* anchor);
+  void ShowAppList(aura::Window* anchor);
+
+  // Dismisses the app list.
+  void DismissAppList();
 
   // Returns app list target visibility.
   bool GetAppListTargetVisibility() const;