Use mojo app list interfaces for mash and classic ash.

ash/mus/shell_delegate_mus.cc

Index: ash/mus/shell_delegate_mus.cc
diff --git a/ash/mus/shell_delegate_mus.cc b/ash/mus/shell_delegate_mus.cc
index 37ec0441027f9871d6161aadd4965ad96bb19fd9..0d0ad7132c3bea83aff7bf277f1d0335be799e0a 100644
--- a/ash/mus/shell_delegate_mus.cc
+++ b/ash/mus/shell_delegate_mus.cc
@@ -146,10 +146,6 @@ void ShellDelegateMus::OpenUrlFromArc(const GURL& url) {
   NOTIMPLEMENTED();
 }
 
-app_list::AppListPresenter* ShellDelegateMus::GetAppListPresenter() {
-  return &app_list_presenter_;
-}
-
 ShelfDelegate* ShellDelegateMus::CreateShelfDelegate(ShelfModel* model) {
   return new ShelfDelegateMus();
 }