Add CanCloseDialog to WebDialogDelegate to allow blocking closing of dialog if needed.

ui/views/controls/webview/web_dialog_view.cc

 // 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 "ui/views/controls/webview/web_dialog_view.h"
 
 #include <vector>
 
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/browser/browser_context.h"
@@ skipping 82 matching lines @@
   return true;
 }
 
 void WebDialogView::ViewHierarchyChanged(
     const ViewHierarchyChangedDetails& details) {
   if (details.is_add && GetWidget())
     InitDialog();
 }
 
 bool WebDialogView::CanClose() {
+  // Don't close UI if |delegate_| does not allow users to close it by
+  // clicking on "x" button or pressing Esc shortcut key on hosting dialog.
+  if (!delegate_->CanCloseDialog() && !close_contents_called_)
+    return false;
+
   // If CloseContents() is called before CanClose(), which is called by
   // RenderViewHostImpl::ClosePageIgnoringUnloadEvents, it indicates
   // beforeunload event should not be fired during closing.
   if ((is_attempting_close_dialog_ && before_unload_fired_) ||
       close_contents_called_) {
     is_attempting_close_dialog_ = false;
     before_unload_fired_ = false;
     return true;
   }
 
@@ skipping 240 matching lines @@
   web_contents->SetDelegate(this);
 
   // Set the delegate. This must be done before loading the page. See
   // the comment above WebDialogUI in its header file for why.
   WebDialogUI::SetDelegate(web_contents, this);
 
   web_view_->LoadInitialURL(GetDialogContentURL());
 }
 
 }  // namespace views