MacViews: Disable NativeWidgetMacTest.WindowModalSheet.

ui/views/widget/native_widget_mac_unittest.mm

 // Copyright 2014 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 "ui/views/widget/native_widget_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #import "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
@@ skipping 1027 matching lines @@
     EXPECT_FALSE(hide_waiter.method_called());
 
     // Wait for the hide again. It will call close on its retained copy of the
     // child NSWindow, but that's fine since all the C++ objects are detached.
     hide_waiter.WaitForMethod();
     EXPECT_TRUE(hide_waiter.method_called());
   }
 }
 
 // Tests behavior of window-modal dialogs, displayed as sheets.
-TEST_F(NativeWidgetMacTest, WindowModalSheet) {
+// Disabled: fails due to sharding adjustments. DCHECK fails during closure when
+// the parent window receives an asynchronous occlusion state change from the
+// window server, after the child has its parent window relationship removed.
+// TODO(tapted): Fix it. http://cbrug.com/666503.
+TEST_F(NativeWidgetMacTest, DISABLED_WindowModalSheet) {
   NSWindow* native_parent =
       MakeNativeParentWithStyle(NSClosableWindowMask | NSTitledWindowMask);
 
   Widget* sheet_widget = views::DialogDelegate::CreateDialogWidget(
       new ModalDialogDelegate(ui::MODAL_TYPE_WINDOW), nullptr,
       [native_parent contentView]);
 
   // Retain, to run checks after the Widget is torn down.
   base::scoped_nsobject<NSWindow> sheet_window(
       [sheet_widget->GetNativeWindow() retain]);
@@ skipping 772 matching lines @@
 
 - (void)dealloc {
   if (deallocFlag_) {
     DCHECK(!*deallocFlag_);
     *deallocFlag_ = true;
   }
   [super dealloc];
 }
 
 @end