[Showcase] Load Roboto as Typography font

ios/showcase/core/app_delegate.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/app_delegate.h"
 
 #import "ios/showcase/core/showcase_model.h"
 #import "ios/showcase/core/showcase_view_controller.h"
+#import "ios/third_party/material_components_ios/src/components/Typography/src/MaterialTypography.h"
+#import "ios/third_party/material_roboto_font_loader_ios/src/src/MDCTypographyAdditions/MDFRobotoFontLoader+MDCTypographyAdditions.h"
+#import "ios/third_party/material_roboto_font_loader_ios/src/src/MaterialRobotoFontLoader.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @implementation AppDelegate
 @synthesize window = _window;
 
 - (BOOL)application:(UIApplication*)application
     didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {
-  // Override point for customization after application launch.
+  [MDCTypography setFontLoader:[MDFRobotoFontLoader sharedInstance]];
   self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
   ShowcaseViewController* viewController =
       [[ShowcaseViewController alloc] initWithRows:[self rowsToDisplay]];
   UINavigationController* navigationController = [[UINavigationController alloc]
       initWithRootViewController:viewController];
   self.window.rootViewController = navigationController;
   [self.window makeKeyAndVisible];
   return YES;
 }
 
 #pragma mark - Private
 
 // Creates model data to display in the view controller.
 - (NSArray<showcase::ModelRow*>*)rowsToDisplay {
   NSArray<showcase::ModelRow*>* rows = [ShowcaseModel model];
   NSSortDescriptor* sortDescriptor =
       [NSSortDescriptor sortDescriptorWithKey:showcase::kClassForDisplayKey
                                     ascending:YES];
   return [rows sortedArrayUsingDescriptors:@[ sortDescriptor ]];
 }
 
 @end