Add NTPViewController to Showcase.

ios/showcase/core/showcase_model.mm

 // Copyright 2016 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.
 
 #import "ios/showcase/core/showcase_model.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @implementation ShowcaseModel
 
 // Insert additional rows in this array. All rows will be sorted upon
 // import into Showcase.
 // |kShowcaseClassForDisplayKey| and |kShowcaseClassForInstantiationKey| are
 // required. |kShowcaseUseCaseKey| is optional.
 + (NSArray<showcase::ModelRow*>*)model {
   return @[
     @{
       showcase::kClassForDisplayKey : @"ContentSuggestionsViewController",
       showcase::kClassForInstantiationKey : @"SCContentSuggestionsCoordinator",
       showcase::kUseCaseKey : @"Content Suggestions UI",
     },
     @{
       showcase::kClassForDisplayKey : @"MenuViewController",
       showcase::kClassForInstantiationKey : @"MenuViewController",
       showcase::kUseCaseKey : @"Tools menu",
     },
     @{
+      showcase::kClassForDisplayKey : @"NTPViewController",
+      showcase::kClassForInstantiationKey : @"SCNTPCoordinator",
+      showcase::kUseCaseKey : @"NTP",
+    },
+    @{
       showcase::kClassForDisplayKey : @"PaymentRequestEditViewController",
       showcase::kClassForInstantiationKey : @"SCPaymentsEditorCoordinator",
       showcase::kUseCaseKey : @"Generic payment request editor",
     },
     @{
       showcase::kClassForDisplayKey : @"PaymentRequestPickerViewController",
       showcase::kClassForInstantiationKey : @"SCPaymentsPickerCoordinator",
       showcase::kUseCaseKey : @"Payment request picker view",
     },
     @{
@@ skipping 23 matching lines @@
     },
     @{
       showcase::kClassForDisplayKey : @"UITableViewCell",
       showcase::kClassForInstantiationKey : @"UIKitTableViewCellViewController",
       showcase::kUseCaseKey : @"UIKit Table Cells",
     },
   ];
 }
 
 @end