Add deprecation warning banner to App Launcher on Mac.

ui/app_list/app_list_view_delegate.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/app_list/app_list_view_delegate.h"
 
 namespace app_list {
 
 AppListViewDelegate::User::User() : active(false) {
 }
 
 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(
+    size_t* message_break) const {
+  *message_break = 0;
+  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