Fix an ODR violation for ModalDialogDelegate found by ASan

ui/views/widget/desktop_aura/desktop_native_widget_aura_unittest.cc

 // Copyright 2013 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/widget/desktop_aura/desktop_native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
 #include "build/build_config.h"
@@ skipping 491 matching lines @@
 // Verifies deleting the widget from a mouse pressed event doesn't crash.
 TEST_F(DesktopAuraWidgetTest, CloseWidgetDuringMousePress) {
   RunCloseWidgetDuringDispatchTest(this, ui::ET_MOUSE_PRESSED);
 }
 
 // Verifies deleting the widget from a mouse released event doesn't crash.
 TEST_F(DesktopAuraWidgetTest, CloseWidgetDuringMouseReleased) {
   RunCloseWidgetDuringDispatchTest(this, ui::ET_MOUSE_RELEASED);
 }
 
+namespace {
+
 // Provides functionality to create a window modal dialog.
 class ModalDialogDelegate : public DialogDelegateView {
  public:
   ModalDialogDelegate() {}
   ~ModalDialogDelegate() override {}
 
   // WidgetDelegate overrides.
   ui::ModalType GetModalType() const override { return ui::MODAL_TYPE_WINDOW; }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ModalDialogDelegate);
 };
 
+}  // namespace
+
 // This test verifies that whether mouse events when a modal dialog is
 // displayed are eaten or recieved by the dialog.
 TEST_F(WidgetTest, WindowMouseModalityTest) {
   // Create a top level widget.
   Widget top_level_widget;
   Widget::InitParams init_params =
       CreateParams(Widget::InitParams::TYPE_WINDOW);
   init_params.show_state = ui::SHOW_STATE_NORMAL;
   gfx::Rect initial_bounds(0, 0, 500, 500);
   init_params.bounds = initial_bounds;
@@ skipping 119 matching lines @@
   target->HandleKeyboardMessage(WM_CHAR, 0, 0, &handled);
   target->HandleKeyboardMessage(WM_SYSCHAR, 0, 0, &handled);
   target->HandleKeyboardMessage(WM_SYSDEADCHAR, 0, 0, &handled);
   widget.CloseNow();
 }
 
 #endif  // defined(OS_WIN)
 
 }  // namespace test
 }  // namespace views