Refactor creation of SadTabView into a tab helper object

ios/chrome/browser/web/sad_tab_tab_helper.h

Index: ios/chrome/browser/web/sad_tab_tab_helper.h
diff --git a/ios/chrome/browser/web/sad_tab_tab_helper.h b/ios/chrome/browser/web/sad_tab_tab_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..55f83f440a3958097f886a7794face7b659a293e
--- /dev/null
+++ b/ios/chrome/browser/web/sad_tab_tab_helper.h
@@ -0,0 +1,35 @@
+// 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/tab_helper_delegate.h"
+#import "ios/web/public/web_state/web_state_observer.h"
+#import "ios/web/public/web_state/web_state_user_data.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+class SadTabTabHelper : public web::WebStateUserData<SadTabTabHelper>,

[kkhorimoto, 2017/04/10 22:31:09]

Please add comments for this class

[PL, 2017/04/11 01:35:21]

Done, thanks!

+                        public web::WebStateObserver {
+ public:
+  explicit SadTabTabHelper(web::WebState* web_state);
+  SadTabTabHelper(web::WebState* web_state, id<TabHelperDelegate> delegate);
+  ~SadTabTabHelper() override;

[kkhorimoto, 2017/04/10 22:31:10]

If we want to enforce that this object is created via the static method below,
let's move the constructors/destructor into private below.  Also, pease add
comments to these functions.

[PL, 2017/04/11 01:35:21]

Done: I don't need the first one, so I've taken that out and added a comment to
the constructor and deconstructor.

+
+  static void CreateForWebState(web::WebState* web_state,

[kkhorimoto, 2017/04/10 22:31:09]

Needs a comment.

[PL, 2017/04/11 01:35:21]

Done, thank you!

+                                id<TabHelperDelegate> delegate);
+
+  // A TabHelperDelegate that can control aspects of this tab helper's behavior
+  __weak id<TabHelperDelegate> delegate;

[kkhorimoto, 2017/04/10 22:31:10]

C++ ivars require a trailing underscore.  Also, we typically don't expose ivars
publicly; can you move the ivar to the private portion of this class?  Also,
since we're setting the delegate in the constructor, do we even need to expose
getters/setters?  It seems like the delegate is only used internally within this
helper.

[Eugene But (OOO till 7-30), 2017/04/10 22:56:28]

More on Access Control here:
https://google.github.io/styleguide/cppguide.html#Access_Control

[PL, 2017/04/11 01:35:21]

Done! I've made the delegate variable private. I'm not sure which getter/setter
I might be able to move though, let me know if I've missed something here.

+
+ private:
+  // Presents a new SadTabView via the web_state object
+  void presentSadTab(const GURL& urlCausingFailure);

[kkhorimoto, 2017/04/10 22:31:09]

s/urlCausingFailure/url_causing_failure

[kkhorimoto, 2017/04/10 22:31:10]

s/presentSadTab/PresentSadTab

[PL, 2017/04/11 01:35:21]

Done. My Objective-C is showing, thanks!

+
+  // An overridden callback that notifies SadTabTabHelper of a renderer crash
+  // via the web_state_observer superclass
+  void RenderProcessGone() override;

[kkhorimoto, 2017/04/10 22:31:09]

Typically for overridden functions, we just comment with the superclass's name
(see
https://cs.chromium.org/chromium/src/ios/web/navigation/navigation_manager_im...
for example)

[PL, 2017/04/11 01:35:21]

Done, thanks!

+
+  NSString* helperID();
+};