MacViews: Remove constrained window dependencies for certificate viewer.

chrome/browser/ui/cocoa/single_web_contents_dialog_manager_cocoa.mm

 // Copyright 2015 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/single_web_contents_dialog_manager_cocoa.h"
 
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_mac.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_sheet_controller.h"
 #include "components/web_modal/web_contents_modal_dialog_host.h"
@@ skipping 27 matching lines @@
     return;
 
   NSView* parent_view = host_->GetHostView();
   // Note that simply [parent_view window] for an inactive tab is nil. However,
   // the following should always be non-nil for all WebContents containers.
   NSWindow* parent_window =
       delegate_->GetWebContents()->GetTopLevelNativeWindow();
 
   [[ConstrainedWindowSheetController controllerForParentWindow:parent_window]
       showSheet:sheet_ forParentView:parent_view];
+  dialog();
 }
 
 void SingleWebContentsDialogManagerCocoa::Hide() {
   NSWindow* parent_window =
       delegate_->GetWebContents()->GetTopLevelNativeWindow();
   [[ConstrainedWindowSheetController controllerForParentWindow:parent_window]
       hideSheet:sheet_];
 }
 
 void SingleWebContentsDialogManagerCocoa::Close() {
@@ skipping 18 matching lines @@
     web_modal::WebContentsModalDialogHost* new_host) {
   // No need to observe the host. For Cocoa, the constrained window controller
   // will reposition the dialog when necessary. The host can also never change.
   // Tabs showing a dialog can not be dragged off a Cocoa browser window.
   // However, closing a tab with a dialog open will set the host back to null.
   DCHECK_NE(!!host_, !!new_host);
   host_ = new_host;
 }
 
 gfx::NativeWindow SingleWebContentsDialogManagerCocoa::dialog() {
-  return [sheet_ sheetWindow];
+  // Update |dialog_| if unpopulated or if the sheetWindow has changed.
+  if (!dialog_ || ([sheet_ sheetWindow] && dialog_ != [sheet_ sheetWindow]))
+    dialog_ = [sheet_ sheetWindow];
+  return dialog_;
 }