Add deprecation warning banner to App Launcher on Mac.

ui/app_list/app_list_view_delegate.cc

Index: ui/app_list/app_list_view_delegate.cc
diff --git a/ui/app_list/app_list_view_delegate.cc b/ui/app_list/app_list_view_delegate.cc
index 7ec19b73856bfc55a1dd4351977813589f1852e6..d7d7beeaa62d0583a0f055352b658408f491d195 100644
--- a/ui/app_list/app_list_view_delegate.cc
+++ b/ui/app_list/app_list_view_delegate.cc
@@ -13,4 +13,26 @@ AppListViewDelegate::User::User(const User& other) = default;
 
 AppListViewDelegate::User::~User() {}
 
-}  // app_list
+#if !defined(OS_CHROMEOS)
+base::string16 AppListViewDelegate::GetMessageTitle() const {
+  return base::string16();
+}
+base::string16 AppListViewDelegate::GetMessageText() const {
+  return base::string16();
+}
+base::string16 AppListViewDelegate::GetAppsShortcutName() const {
+  return base::string16();
+}
+base::string16 AppListViewDelegate::GetLearnMoreText() const {
+  return base::string16();
+}
+base::string16 AppListViewDelegate::GetLearnMoreLink() const {
+  return base::string16();
+}
+gfx::ImageSkia* AppListViewDelegate::GetAppsIcon() const {
+  return nullptr;
+}
+void AppListViewDelegate::OpenLearnMoreLink() {}
+#endif
+
+}  // namespace app_list