linux-aura: Restore middle-click on new-tab button behaviour.

chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm

 // Copyright (c) 2012 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 "chrome/browser/ui/cocoa/tabs/tab_strip_controller.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 657 matching lines @@
   [[controller view] setHidden:YES];
 
   return controller;
 }
 
 // (Private) Handles a click on the new tab button.
 - (void)clickNewTabButton:(id)sender {
   content::RecordAction(UserMetricsAction("NewTab_Button"));
   UMA_HISTOGRAM_ENUMERATION("Tab.NewTab", TabStripModel::NEW_TAB_BUTTON,
                             TabStripModel::NEW_TAB_ENUM_COUNT);
-  tabStripModel_->delegate()->AddBlankTabAt(-1, true);
+  tabStripModel_->delegate()->AddURLTabAt(GURL(), -1, true);
 }
 
 // (Private) Returns the number of open tabs in the tab strip. This is the
 // number of TabControllers we know about (as there's a 1-to-1 mapping from
 // these controllers to a tab) less the number of closing tabs.
 - (NSInteger)numberOfOpenTabs {
   return static_cast<NSInteger>(tabStripModel_->count());
 }
 
 // (Private) Returns the number of open, mini-tabs.
@@ skipping 1528 matching lines @@
 NSView* GetSheetParentViewForWebContents(WebContents* web_contents) {
   // View hierarchy of the contents view:
   // NSView  -- switchView, same for all tabs
   // +- NSView  -- TabContentsController's view
   //    +- TabContentsViewCocoa
   //
   // Changing it? Do not forget to modify
   // -[TabStripController swapInTabAtIndex:] too.
   return [web_contents->GetView()->GetNativeView() superview];
 }