[Reland] Enable AutoResize for Constrained Web Dialogs for Mac.

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 40 matching lines @@
   NSWindow* parent_window =
       delegate_->GetWebContents()->GetTopLevelNativeWindow();
   [[ConstrainedWindowSheetController controllerForParentWindow:parent_window]
       hideSheet];
 }
 
 void SingleWebContentsDialogManagerCocoa::Close() {
   [[ConstrainedWindowSheetController controllerForSheet:sheet_]
       closeSheet:sheet_];
   client_->set_manager(nullptr);
+  bool dialog_was_open = client_->DialogWasShown();
   client_->OnDialogClosing();      // |client_| might delete itself here.
-  delegate_->WillClose(dialog());  // Deletes |this|.
+  if (dialog_was_open)
+    delegate_->WillClose(dialog());  // Deletes |this|.
 }
 
 void SingleWebContentsDialogManagerCocoa::Focus() {
 }
 
 void SingleWebContentsDialogManagerCocoa::Pulse() {
   [[ConstrainedWindowSheetController controllerForSheet:sheet_]
       pulseSheet:sheet_];
 }
 
 void SingleWebContentsDialogManagerCocoa::HostChanged(
     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];
 }