Refactor creation of SadTabView into a tab helper object

ios/chrome/browser/web/sad_tab_tab_helper_delegate.h

Index: ios/chrome/browser/web/sad_tab_tab_helper_delegate.h
diff --git a/ios/chrome/browser/web/sad_tab_tab_helper_delegate.h b/ios/chrome/browser/web/sad_tab_tab_helper_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..ae469bc87d3e6789d17ad26ce5ecf437e920e005
--- /dev/null
+++ b/ios/chrome/browser/web/sad_tab_tab_helper_delegate.h
@@ -0,0 +1,26 @@
+// 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.
+
+#ifndef tab_helper_delegate_h

[sdefresne, 2017/04/11 08:17:39]

This is not using the correct header guards. Please use src/tools/boilerplate.py
script to create file with the correct header guards.

[peterlaurens, 2017/04/11 21:57:27]

Done! Thanks!

+#define tab_helper_delegate_h
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+class SadTabTabHelper;
+
+// SadTabTabHelperDelegate defines an interface that allows SadTabTabHelper
+// instances to learn about the visibility of the Tab they are helping.
+@protocol SadTabTabHelperDelegate<NSObject>
+
+// Returns whether the tab for the tab helper is visible, allowing differences

[Eugene But (OOO till 7-30), 2017/04/11 15:17:00]

Do you want to elaborate what |visible| means in this context (app is in active
state and tab is the frontmost)?

[peterlaurens, 2017/04/11 21:57:27]

Done!

+// in the behavior of the helper for visible vs. non-visible tabs.
+- (BOOL)isTabVisibleForTabHelper:(SadTabTabHelper*)tabHelper;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif /* tab_helper_delegate_h */