Use the old back button on Terms of Service.

ios/chrome/browser/ui/first_run/static_file_view_controller.mm

 // 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 "ios/chrome/browser/ui/first_run/static_file_view_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #include "base/logging.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+#import "ios/chrome/browser/ui/icons/chrome_icon.h"
 #import "ios/chrome/browser/ui/material_components/utils.h"
 #include "ios/chrome/browser/ui/rtl_geometry.h"
 #import "ios/third_party/material_components_ios/src/components/AppBar/src/MaterialAppBar.h"
 #import "ios/third_party/material_components_ios/src/components/FlexibleHeader/src/MaterialFlexibleHeader.h"
 #import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
 #import "ios/web/public/web_view_creation_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @interface StaticFileViewController ()<UIScrollViewDelegate> {
   ios::ChromeBrowserState* _browserState;  // weak
   NSURL* _URL;
   // YES if the header has been configured for RTL.
   BOOL _headerLaidOutForRTL;
   // The web view used to display the static content.
   WKWebView* _webView;
   // The header.
   MDCAppBar* _appBar;
 }
 

[kkhorimoto, 2017/03/29 20:48:18]

Can we add |-back| to this class's private interface?

[lpromero, 2017/03/30 12:53:48]

Done.

 @end
 
 @implementation StaticFileViewController
 
 - (instancetype)initWithBrowserState:(ios::ChromeBrowserState*)browserState
                                  URL:(NSURL*)URL {
   DCHECK(browserState);
   DCHECK(URL);
   self = [super init];
   if (self) {
@@ skipping 23 matching lines @@
   [_webView setBackgroundColor:[UIColor whiteColor]];
   [self.view addSubview:_webView];
 
   ConfigureAppBarWithCardStyle(_appBar);
   [_appBar headerViewController].headerView.trackingScrollView =
       [_webView scrollView];
   [_webView scrollView].delegate = [_appBar headerViewController];
 
   // Add the app bar at the end.
   [_appBar addSubviewsToParent];
+
+  // Create a custom Back bar button item, as Material Navigation Bar deprecated
+  // the back arrow with a shaft.
+  self.navigationItem.leftBarButtonItem =
+      [ChromeIcon templateBarButtonItemWithImage:[ChromeIcon backIcon]
+                                          target:self
+                                          action:@selector(back)];
+}
+
+#pragma mark - Actions
+
+- (void)back {
+  [self.navigationController popViewControllerAnimated:YES];
 }
 
 @end