Allow dynamic switching in and out of sidetabs mode.

chrome/browser/browser.h

 // Copyright (c) 2010 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_BROWSER_H_
 #define CHROME_BROWSER_BROWSER_H_
 
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 557 matching lines @@
                                                bool defer_load,
                                                SiteInstance* instance) const;
   virtual bool CanDuplicateContentsAt(int index);
   virtual void DuplicateContentsAt(int index);
   virtual void CloseFrameAfterDragSession();
   virtual void CreateHistoricalTab(TabContents* contents);
   virtual bool RunUnloadListenerBeforeClosing(TabContents* contents);
   virtual bool CanCloseContentsAt(int index);
   virtual bool CanBookmarkAllTabs() const;
   virtual void BookmarkAllTabs();
+  virtual bool UseVerticalTabs() const;
+  virtual void ToggleUseVerticalTabs();
 
   // Overridden from TabStripModelObserver:
   virtual void TabInsertedAt(TabContents* contents,
                              int index,
                              bool foreground);
   virtual void TabClosingAt(TabContents* contents, int index);
   virtual void TabDetachedAt(TabContents* contents, int index);
   virtual void TabDeselectedAt(TabContents* contents, int index);
   virtual void TabSelectedAt(TabContents* old_contents,
                              TabContents* new_contents,
@@ skipping 320 matching lines @@
   enum WebAppAction {
     NONE,             // No action at all.
     CREATE_SHORTCUT,  // Bring up create application shortcut dialog.
     UPDATE_SHORTCUT   // Update icon for app shortcut.
   };
 
   // Which deferred action to perform when OnDidGetApplicationInfo is notified
   // from a TabContents. Currently, only one pending action is allowed.
   WebAppAction pending_web_app_action_;
 
+  // Tracks the display mode of the tabstrip.
+  mutable BooleanPrefMember use_vertical_tabs_;
+
   DISALLOW_COPY_AND_ASSIGN(Browser);
 };
 
 #endif  // CHROME_BROWSER_BROWSER_H_