Refactor creation of SadTabView into a tab helper object

ios/chrome/browser/tabs/tab.h

 // Copyright 2012 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.
 
 #ifndef IOS_CHROME_BROWSER_TABS_TAB_H_
 #define IOS_CHROME_BROWSER_TABS_TAB_H_
 
 #import <UIKit/UIKit.h>
 
 #include <memory>
 #include <vector>
 
 #import "components/signin/ios/browser/manage_accounts_delegate.h"
+#import "ios/chrome/browser/web/sad_tab_tab_helper_delegate.h"
 #include "ios/net/request_tracker.h"
 #import "ios/web/public/web_state/ui/crw_web_delegate.h"
 #include "ui/base/page_transition_types.h"
 
 @class AutofillController;
 @class AutoReloadBridge;
 @class CastController;
 @protocol CRWNativeContentProvider;
 @class CRWWebController;
 @class ExternalAppLauncher;
@@ skipping 64 matching lines @@
 
 // The header name and value for the data reduction proxy to request an image to
 // be reloaded without optimizations.
 extern NSString* const kProxyPassthroughHeaderName;
 extern NSString* const kProxyPassthroughHeaderValue;
 
 // Information related to a single tab. The CRWWebController is similar to
 // desktop Chrome's TabContents in that it encapsulates rendering. Acts as the
 // delegate for the CRWWebController in order to process info about pages having
 // loaded.
-@interface Tab : NSObject<CRWWebDelegate, ManageAccountsDelegate>
+@interface Tab
+    : NSObject<CRWWebDelegate, ManageAccountsDelegate, SadTabTabHelperDelegate>
 
 // Browser state associated with this Tab.
 @property(nonatomic, readonly) ios::ChromeBrowserState* browserState;
 
 // TODO(crbug.com/546208): Eliminate this; replace calls with either visible URL
 // or last committed URL, depending on the specific use case.
 // Do not add new calls to this method.
 @property(nonatomic, readonly) const GURL& url;
 
 // The Passkit Dialog provider used to show the UI to download a passkit object.
@@ skipping 236 matching lines @@
 // Evaluates U2F result.
 - (void)evaluateU2FResultFromURL:(const GURL&)url;
 
 // Cancels prerendering. It is an error to call this on anything except a
 // prerender tab (where |isPrerenderTab| is set to YES).
 - (void)discardPrerender;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_TABS_TAB_H_