MacViews: Support MODAL_TYPE_WINDOW in dialog tests.

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 1087 matching lines @@
                   object:native_parent
                    queue:nil
               usingBlock:^(NSNotification* note) {
                 // Ensure that before the sheet runs, the window contents would
                 // be drawn.
                 EXPECT_TRUE(sheet_widget->IsVisible());
                 EXPECT_TRUE(sheet_widget->GetLayer()->IsDrawn());
                 *did_observe_ptr = true;
               }];
 
+  Widget::Widgets children;
+  Widget::GetAllChildWidgets([native_parent contentView], &children);
+  EXPECT_TRUE(children.empty());
+
   sheet_widget->Show();  // Should run the above block, then animate the sheet.
   EXPECT_TRUE(did_observe);
   [[NSNotificationCenter defaultCenter] removeObserver:observer];
 
+  // Ensure sheets are included as a child.
+  Widget::GetAllChildWidgets([native_parent contentView], &children);
+  ASSERT_EQ(1u, children.size());
+  EXPECT_EQ(sheet_widget, *children.begin());
+
   // Modal, so the close button in the parent window should get disabled.
   EXPECT_FALSE([parent_close_button isEnabled]);
 
   // The sheet should be hidden and shown in step with the parent.
   widget_observer.WaitForVisibleCounts(1, 0);
   EXPECT_TRUE(sheet_widget->IsVisible());
 
   // TODO(tapted): Ideally [native_parent orderOut:nil] would also work here.
   // But it does not. AppKit's childWindow management breaks down after an
   // -orderOut: (see BridgedNativeWidget::OnVisibilityChanged()). For regular
@@ skipping 787 matching lines @@
 
 - (void)dealloc {
   if (deallocFlag_) {
     DCHECK(!*deallocFlag_);
     *deallocFlag_ = true;
   }
   [super dealloc];
 }
 
 @end