Mac: Turn on tab overview mode by default.

chrome/browser/ui/browser.cc

 // 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.
 
 #include "chrome/browser/ui/browser.h"
 
 #if defined(OS_WIN)
 #include <shellapi.h>
 #include <windows.h>
 #endif  // OS_WIN
@@ skipping 1377 matching lines @@
   tab_handler_->GetTabStripModel()->SelectNextTab();
 }
 
 void Browser::SelectPreviousTab() {
   UserMetrics::RecordAction(UserMetricsAction("SelectPrevTab"), profile_);
   tab_handler_->GetTabStripModel()->SelectPreviousTab();
 }
 
 void Browser::OpenTabpose() {
 #if defined(OS_MACOSX)
-  if (!CommandLine::ForCurrentProcess()->HasSwitch(
-        switches::kEnableExposeForTabs)) {
-    return;
-  }
-
   UserMetrics::RecordAction(UserMetricsAction("OpenTabpose"), profile_);
   window()->OpenTabpose();
 #else
   NOTREACHED();
 #endif
 }
 
 void Browser::MoveTabNext() {
   UserMetrics::RecordAction(UserMetricsAction("MoveTabNext"), profile_);
   tab_handler_->GetTabStripModel()->MoveTabNext();
@@ skipping 2909 matching lines @@
     // The page transition below is only for the purpose of inserting the tab.
     browser->AddTab(view_source_contents, PageTransition::LINK);
   }
 
   if (profile_->HasSessionService()) {
     SessionService* session_service = profile_->GetSessionService();
     if (session_service)
       session_service->TabRestored(&view_source_contents->controller(), false);
   }
 }