ui/gfx: Get rid of a few static variables from NativeTheme* type.

ui/gfx/native_theme_linux.h

Index: ui/gfx/native_theme_linux.h
diff --git a/ui/gfx/native_theme_linux.h b/ui/gfx/native_theme_linux.h
index 6af1b2f0b2788dac132320f7e0c412c93c5310e9..bb8952b5e329b0f3cf33b2095628a78d32ebcde3 100644
--- a/ui/gfx/native_theme_linux.h
+++ b/ui/gfx/native_theme_linux.h
@@ -16,6 +16,9 @@ class Size;
 // Linux theming API.
 class NativeThemeLinux : public NativeTheme {
  public:
+  NativeThemeLinux();
+  virtual ~NativeThemeLinux();
+
   // Gets our singleton instance.
   static const NativeThemeLinux* instance();
 
@@ -30,9 +33,6 @@ class NativeThemeLinux : public NativeTheme {
                      const ExtraParams& extra) const;
 
  protected:
-  NativeThemeLinux();
-  virtual ~NativeThemeLinux();
-
   // Draw the arrow. Used by scrollbar and inner spin button.
   virtual void PaintArrowButton(
       SkCanvas* gc,