Refactor creation of SadTabView into a tab helper object

ios/chrome/browser/web/sad_tab_tab_helper.mm

+// Copyright 2017 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/chrome/browser/web/sad_tab_tab_helper.h"
+
+#import <Foundation/Foundation.h>
+
+#include "base/strings/sys_string_conversions.h"
+#import "ios/chrome/browser/ui/sad_tab/sad_tab_view.h"
+#import "ios/chrome/browser/web/sad_tab_tab_helper_delegate.h"
+#import "ios/web/public/navigation_manager.h"
+#import "ios/web/public/web_state/ui/crw_generic_content_view.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+DEFINE_WEB_STATE_USER_DATA_KEY(SadTabTabHelper);
+
+SadTabTabHelper::SadTabTabHelper(web::WebState* web_state,
+                                 id<SadTabTabHelperDelegate> delegate)
+    : web::WebStateObserver(web_state), delegate_(delegate) {
+  DCHECK(delegate_);
+}
+
+SadTabTabHelper::~SadTabTabHelper() = default;
+
+void SadTabTabHelper::CreateForWebState(web::WebState* web_state,
+                                        id<SadTabTabHelperDelegate> delegate) {
+  DCHECK(web_state);
+  if (!FromWebState(web_state)) {
+    web_state->SetUserData(UserDataKey(),
+                           new SadTabTabHelper(web_state, delegate));
+  }
+}
+
+void SadTabTabHelper::RenderProcessGone() {
+  if (!delegate_ || [delegate_ isTabVisibleForTabHelper:this]) {
+    PresentSadTab();
+  }
+}
+
+void SadTabTabHelper::PresentSadTab() {
+  SadTabView* sad_tab_view = [[SadTabView alloc] initWithReloadHandler:^{
+    web_state()->GetNavigationManager()->Reload(web::ReloadType::NORMAL, true);
+  }];
+
+  CRWContentView* content_view =
+      [[CRWGenericContentView alloc] initWithView:sad_tab_view];
+
+  web_state()->ShowTransientContentView(content_view);
+}