Get rid of extensions dependency from content\browser.

chrome/browser/tabs/tab_strip_model.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_TABS_TAB_STRIP_MODEL_H_
 #define CHROME_BROWSER_TABS_TAB_STRIP_MODEL_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 23 matching lines @@
 // Each tab may be any one of the following states:
 // . Mini-tab. Mini tabs are locked to the left side of the tab strip and
 //   rendered differently (small tabs with only a favicon). The model makes
 //   sure all mini-tabs are at the beginning of the tab strip. For example,
 //   if a non-mini tab is added it is forced to be with non-mini tabs. Requests
 //   to move tabs outside the range of the tab type are ignored. For example,
 //   a request to move a mini-tab after non-mini-tabs is ignored.
 //   You'll notice there is no explcit api for making a tab a mini-tab, rather
 //   there are two tab types that are implicitly mini-tabs:
 //   . App. Corresponds to an extension that wants an app tab. App tabs are
-//     identified by TabContents::is_app(). App tabs are always pinneded (you
-//     can't unpin them).
+//     identified by TabContentsWrapper::extension_tab_helper()::is_app().
+//     App tabs are always pinneded (you can't unpin them).
 //   . Pinned. Any tab can be pinned. Non-app tabs whose pinned state is changed
 //     are moved to be with other mini-tabs or non-mini tabs.
 //
 //  A TabStripModel has one delegate that it relies on to perform certain tasks
 //  like creating new TabStripModels (probably hosted in Browser windows) when
 //  required. See TabStripDelegate above for more information.
 //
 //  A TabStripModel also has N observers (see TabStripModelObserver above),
 //  which can be registered via Add/RemoveObserver. An Observer is notified of
 //  tab creations, removals, moves, and other interesting events. The
@@ skipping 575 matching lines @@
 
   // A scoped container for notification registries.
   NotificationRegistrar registrar_;
 
   TabStripSelectionModel selection_model_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TabStripModel);
 };
 
 #endif  // CHROME_BROWSER_TABS_TAB_STRIP_MODEL_H_