Add NTPViewController to Showcase.

ios/showcase/tab_grid/sc_tab_grid_coordinator.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/tab_grid/sc_tab_grid_coordinator.h"
 
 #import "base/format_macros.h"
+#import "ios/clean/chrome/browser/ui/commands/settings_commands.h"

[lpromero, 2017/04/13 17:04:57]

I am moving this in its own CL as this fixes a Showcase issue.

 #import "ios/clean/chrome/browser/ui/commands/tab_grid_commands.h"
 #import "ios/clean/chrome/browser/ui/tab_collection/tab_collection_data_source.h"
 #import "ios/clean/chrome/browser/ui/tab_grid/tab_grid_view_controller.h"
 #import "ios/showcase/common/protocol_alerter.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @interface SCTabGridCoordinator ()<TabCollectionDataSource>
@@ skipping 30 matching lines @@
 
 - (NSString*)titleAtIndex:(int)index {
   return [NSString stringWithFormat:@"Tab %d", index];
 }
 
 - (int)indexOfActiveTab {
   return kTabCollectionDataSourceInvalidIndex;
 }
 
 @end