Reuse NativeThemeAuraDark for cros tray.

ui/views/view.h

 // 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.
 
 #ifndef UI_VIEWS_VIEW_H_
 #define UI_VIEWS_VIEW_H_
 
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 513 matching lines @@
   const ui::ThemeProvider* GetThemeProvider() const;
 
   // Returns the NativeTheme to use for this View. This calls through to
   // GetNativeTheme() on the Widget this View is in, or provides a default
   // theme if there's no widget. Warning: the default theme might not be
   // correct; you should probably override OnNativeThemeChanged().
   ui::NativeTheme* GetNativeTheme() {
     return const_cast<ui::NativeTheme*>(
         const_cast<const View*>(this)->GetNativeTheme());
   }
-  const ui::NativeTheme* GetNativeTheme() const;
+  virtual const ui::NativeTheme* GetNativeTheme() const;
 
   // RTL painting --------------------------------------------------------------
 
   // This method determines whether the gfx::Canvas object passed to
   // View::Paint() needs to be transformed such that anything drawn on the
   // canvas object during View::Paint() is flipped horizontally.
   //
   // By default, this function returns false (which is the initial value of
   // |flip_canvas_on_paint_for_rtl_ui_|). View subclasses that need to paint on
   // a flipped gfx::Canvas when the UI layout is right-to-left need to call
@@ skipping 1024 matching lines @@
   // Belongs to this view, but it's reference-counted on some platforms
   // so we can't use a scoped_ptr. It's dereferenced in the destructor.
   NativeViewAccessibility* native_view_accessibility_;
 
   DISALLOW_COPY_AND_ASSIGN(View);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_H_