Reuse NativeThemeAuraDark for cros tray.

ui/views/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.
 
 #define _USE_MATH_DEFINES // For VC++ to get M_PI. This has to be first.
 
 #include "ui/views/view.h"
 
 #include <algorithm>
 #include <cmath>
@@ skipping 856 matching lines @@
 void View::SetBorder(std::unique_ptr<Border> b) {
   border_ = std::move(b);
 }
 
 const ui::ThemeProvider* View::GetThemeProvider() const {
   const Widget* widget = GetWidget();
   return widget ? widget->GetThemeProvider() : nullptr;
 }
 
 const ui::NativeTheme* View::GetNativeTheme() const {
+  if (parent())
+    return parent()->GetNativeTheme();
+
   const Widget* widget = GetWidget();
   if (widget)
     return widget->GetNativeTheme();
 
 #if defined(OS_WIN)
   // On Windows, ui::NativeTheme::GetInstanceForWeb() returns NativeThemeWinAura
   // because that's what the renderer wants, but Views should default to
   // NativeThemeWin. TODO(estade): clean this up, see http://crbug.com/558029
   return ui::NativeThemeWin::instance();
 #else
@@ skipping 1539 matching lines @@
   // Message the RootView to do the drag and drop. That way if we're removed
   // the RootView can detect it and avoid calling us back.
   gfx::Point widget_location(event.location());
   ConvertPointToWidget(this, &widget_location);
   widget->RunShellDrag(this, data, widget_location, drag_operations, source);
   // WARNING: we may have been deleted.
   return true;
 }
 
 }  // namespace views