Create CoreTabHelper, move remaining core TCW functionality into it.

chrome/browser/ui/alternate_error_tab_observer.h

+// Copyright (c) 2011 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 CHROME_BROWSER_UI_ALTERNATE_ERROR_TAB_OBSERVER_H_
+#define CHROME_BROWSER_UI_ALTERNATE_ERROR_TAB_OBSERVER_H_
+#pragma once
+
+#include "chrome/browser/prefs/pref_change_registrar.h"
+#include "content/browser/tab_contents/tab_contents_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class TabContentsWrapper;
+
+// Per-tab class to handle functionality that is core to the operation of tabs.

[Jói, 2011/12/09 12:36:47]

I think this is copy-pasted from the original change, probably needs to be
updated?

[Avi (use Gerrit), 2011/12/09 16:12:11]

Indeed.

+class AlternateErrorPageTabObserver : public TabContentsObserver,
+                                      public content::NotificationObserver {
+ public:
+  explicit AlternateErrorPageTabObserver(TabContentsWrapper* wrapper);
+  virtual ~AlternateErrorPageTabObserver();
+
+  static void RegisterUserPrefs(PrefService* prefs);
+
+ private:
+  // TabContentsObserver overrides:
+  virtual void RenderViewCreated(RenderViewHost* render_view_host) OVERRIDE;
+
+  // content::NotificationObserver overrides:
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  // Internal helpers ----------------------------------------------------------
+
+  // Returns the server that can provide alternate error pages.  If the returned
+  // URL is empty, the default error page built into WebKit will be used.
+  GURL GetAlternateErrorPageURL() const;
+
+  // Send the alternate error page URL to the renderer.
+  void UpdateAlternateErrorPageURL(RenderViewHost* rvh);
+
+  // Our owning TabContentsWrapper.
+  TabContentsWrapper* wrapper_;
+
+  content::NotificationRegistrar registrar_;
+  PrefChangeRegistrar pref_change_registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(AlternateErrorPageTabObserver);
+};
+
+#endif  // CHROME_BROWSER_UI_ALTERNATE_ERROR_TAB_OBSERVER_H_