Rejigger ThemeService: move exposure of ThemeProvider interface to a

ui/base/default_theme_provider.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_BASE_DEFAULT_THEME_PROVIDER_H_
 #define UI_BASE_DEFAULT_THEME_PROVIDER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/base/theme_provider.h"
 #include "ui/base/ui_base_export.h"
 
 namespace ui {
 class ResourceBundle;
 }
 
 namespace ui {
 
 class UI_BASE_EXPORT DefaultThemeProvider : public ThemeProvider {
  public:
   DefaultThemeProvider();
   ~DefaultThemeProvider() override;
 
   // Overridden from ui::ThemeProvider:
-  bool UsingSystemTheme() const override;
   gfx::ImageSkia* GetImageSkiaNamed(int id) const override;
   SkColor GetColor(int id) const override;
   int GetDisplayProperty(int id) const override;
   bool ShouldUseNativeFrame() const override;
   bool HasCustomImage(int id) const override;
   base::RefCountedMemory* GetRawData(int id, ui::ScaleFactor scale_factor)
       const override;
 
 #if defined(OS_MACOSX)
+  bool UsingSystemTheme() const override;
   NSImage* GetNSImageNamed(int id) const override;
   NSColor* GetNSImageColorNamed(int id) const override;
   NSColor* GetNSColor(int id) const override;
   NSColor* GetNSColorTint(int id) const override;
   NSGradient* GetNSGradient(int id) const override;
 #endif
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultThemeProvider);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DEFAULT_THEME_PROVIDER_H_