ui: Move NativeTheme files into ui/base/native_theme/ directory.

ui/base/native_theme/native_theme.cc

Index: ui/base/native_theme/native_theme.cc
diff --git a/ui/gfx/native_theme.cc b/ui/base/native_theme/native_theme.cc
similarity index 89%
rename from ui/gfx/native_theme.cc
rename to ui/base/native_theme/native_theme.cc
index 331d429ba258235de1a06f223ab58284ab9cdc5e..1853826f195dc7599ef6fdd3931bfae5043c45bb 100644
--- a/ui/gfx/native_theme.cc
+++ b/ui/base/native_theme/native_theme.cc
@@ -2,11 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "ui/gfx/native_theme.h"
+#include "ui/base/native_theme/native_theme.h"
 
-#include "ui/gfx/size.h"
-
-namespace gfx {
+namespace ui {
 
 unsigned int NativeTheme::thumb_inactive_color_ = 0xeaeaea;
 unsigned int NativeTheme::thumb_active_color_ = 0xf4f4f4;
@@ -23,4 +21,4 @@ void NativeTheme::SetScrollbarColors(unsigned inactive_color,
 // NativeTheme::instance() is implemented in the platform specific source files,
 // such as native_theme_win.cc or native_theme_linux.cc
 
-}  // namespace gfx
+}  // namespace ui