Dismiss action in tab modal dialogs.

chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.h"
 
 #include "base/mac/scoped_nsobject.h"
 #include "chrome/browser/ui/browser_dialogs.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_alert.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
@@ skipping 39 matching lines @@
   WindowOpenDisposition disposition =
       ui::WindowOpenDispositionFromNSEvent([NSApp currentEvent]);
   delegate_->LinkClicked(disposition);
 }
 
 @end
 
 TabModalConfirmDialogMac::TabModalConfirmDialogMac(
     TabModalConfirmDialogDelegate* delegate,
     content::WebContents* web_contents)
-    : delegate_(delegate) {
+    : closing_(false),
+      delegate_(delegate) {
   bridge_.reset([[TabModalConfirmDialogMacBridge alloc]
       initWithDelegate:delegate]);
 
   alert_.reset([[ConstrainedWindowAlert alloc] init]);
   [alert_ setMessageText:
       l10n_util::FixUpWindowsStyleLabel(delegate->GetTitle())];
   [alert_ setLinkText:l10n_util::FixUpWindowsStyleLabel(
                           delegate->GetLinkText())
                target:bridge_
                action:@selector(onLinkClicked:)];
@@ skipping 25 matching lines @@
 
 void TabModalConfirmDialogMac::AcceptTabModalDialog() {
   delegate_->Accept();
 }
 
 void TabModalConfirmDialogMac::CancelTabModalDialog() {
   delegate_->Cancel();
 }
 
 void TabModalConfirmDialogMac::CloseDialog() {
-  window_->CloseWebContentsModalDialog();
+  if (!closing_) {
+    closing_ = true;
+    window_->CloseWebContentsModalDialog();
+  }
 }
 
 void TabModalConfirmDialogMac::OnConstrainedWindowClosed(
     ConstrainedWindowMac* window) {
+  // Provide a disposition in case the dialog was closed without accepting or
+  // cancelling.
+  delegate_->Close();
   delete this;
 }