Use a standard message box for DesktopCastingWarningView.

chrome/browser/ui/views/simple_message_box_views.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 "chrome/browser/ui/simple_message_box.h"
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 55 matching lines @@
   base::string16 yes_text_;
   base::string16 no_text_;
   MessageBoxResult* result_;
   views::MessageBoxView* message_box_view_;
   base::Closure quit_runloop_;
   bool is_system_modal_;
 
   DISALLOW_COPY_AND_ASSIGN(SimpleMessageBoxViews);
 };
 
+// The currently showing message box, if there is one. Used for tests.
+SimpleMessageBoxViews* g_current_message_box = nullptr;
+
 ////////////////////////////////////////////////////////////////////////////////
 // SimpleMessageBoxViews, public:
 
 SimpleMessageBoxViews::SimpleMessageBoxViews(
     const base::string16& title,
     const base::string16& message,
     MessageBoxType type,
     const base::string16& yes_text,
     const base::string16& no_text,
     const base::string16& checkbox_text,
@@ skipping 19 matching lines @@
   if (!checkbox_text.empty()) {
     message_box_view_->SetCheckBoxLabel(checkbox_text);
     message_box_view_->SetCheckBoxSelected(true);
   }
 }
 
 SimpleMessageBoxViews::~SimpleMessageBoxViews() {
 }
 
 MessageBoxResult SimpleMessageBoxViews::RunDialogAndGetResult() {
+  g_current_message_box = this;

[msw, 2016/10/27 21:46:45]

Should this care if there's any other dialog already showing?

[Evan Stade, 2016/10/28 17:31:55]

Given how it's presently used (only for testing), I guess not? Do you think it
should?

   MessageBoxResult result = MESSAGE_BOX_RESULT_NO;
   result_ = &result;
   // TODO(pkotwicz): Exit message loop when the dialog is closed by some other
   // means than |Cancel| or |Accept|. crbug.com/404385
   base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
   base::MessageLoopForUI::ScopedNestableTaskAllower allow_nested(loop);
   base::RunLoop run_loop;
   quit_runloop_ = run_loop.QuitClosure();
   run_loop.Run();
+  g_current_message_box = nullptr;
   return result;
 }
 
 int SimpleMessageBoxViews::GetDialogButtons() const {
   if (type_ == MESSAGE_BOX_TYPE_QUESTION)
     return ui::DIALOG_BUTTON_OK | ui::DIALOG_BUTTON_CANCEL;
 
   return ui::DIALOG_BUTTON_OK;
 }
 
@@ skipping 106 matching lines @@
                                 checkbox_text, !parent /* is_system_modal */);
   constrained_window::CreateBrowserModalDialogViews(dialog, parent)->Show();
 
   // NOTE: |dialog| may have been deleted by the time |RunDialogAndGetResult()|
   // returns.
   return dialog->RunDialogAndGetResult();
 }
 
 }  // namespace
 
+bool CloseMessageBoxForTest(bool accept) {
+  if (!g_current_message_box)
+    return false;
+
+  if (accept)
+    g_current_message_box->Accept();
+  else
+    g_current_message_box->Cancel();
+  return true;
+}
+
 void ShowWarningMessageBox(gfx::NativeWindow parent,
                            const base::string16& title,
                            const base::string16& message) {
   ShowMessageBoxImpl(parent, title, message, MESSAGE_BOX_TYPE_WARNING,
                      base::string16(), base::string16(), base::string16());
 }
 
 bool ShowWarningMessageBoxWithCheckbox(gfx::NativeWindow parent,
                                        const base::string16& title,
                                        const base::string16& message,
@@ skipping 14 matching lines @@
 MessageBoxResult ShowMessageBoxWithButtonText(gfx::NativeWindow parent,
                                               const base::string16& title,
                                               const base::string16& message,
                                               const base::string16& yes_text,
                                               const base::string16& no_text) {
   return ShowMessageBoxImpl(parent, title, message, MESSAGE_BOX_TYPE_QUESTION,
                             yes_text, no_text, base::string16());
 }
 
 }  // namespace chrome