Fix dragging a tab out of a window when the only tabs left behind are phantom...

chrome/browser/cocoa/tab_window_controller.mm

 // 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.
 
 #import "chrome/browser/cocoa/tab_window_controller.h"
 
 #include "app/theme_provider.h"
 #include "base/logging.h"
 #import "chrome/browser/cocoa/tab_strip_view.h"
 #import "chrome/browser/cocoa/themed_window.h"
@@ skipping 201 matching lines @@
   // subclass must implement
   NOTIMPLEMENTED();
 }
 
 - (NSInteger)numberOfTabs {
   // subclass must implement
   NOTIMPLEMENTED();
   return 0;
 }
 
+- (BOOL)hasLiveTabs {
+  // subclass must implement
+  NOTIMPLEMENTED();
+  return NO;
+}
+
 - (NSString*)selectedTabTitle {
   // subclass must implement
   NOTIMPLEMENTED();
   return @"";
 }
 
 - (BOOL)hasTabStrip {
   // Subclasses should implement this.
   NOTIMPLEMENTED();
   return YES;
@@ skipping 11 matching lines @@
 }
 
 // Tell the window that it needs to call performClose: as soon as the current
 // drag is complete. This prevents a window (and its overlay) from going away
 // during a drag.
 - (void)deferPerformClose {
   closeDeferred_ = YES;
 }
 
 @end