Move the "platform" wrappers in skia/ext to the skia namespace.

base/gfx/native_theme.h

Index: base/gfx/native_theme.h
===================================================================
--- base/gfx/native_theme.h	(revision 6968)
+++ base/gfx/native_theme.h	(working copy)
@@ -17,9 +17,12 @@
 #include "base/gfx/size.h"
 #include "skia/include/SkColor.h"
 
-namespace gfx {
+namespace skia {
 class PlatformCanvasWin;
+}  // namespace skia
 
+namespace gfx {
+
 // TODO: Define class member enums to replace part_id and state_id parameters
 // that are currently defined in <vssym32.h>. Afterward, classic_state should
 // be removed and class users wouldn't need to include <vssym32.h> anymore.
@@ -128,7 +131,7 @@
                               int classic_state,
                               RECT* target_rect,
                               RECT* align_rect,
-                              PlatformCanvasWin* canvas) const;
+                              skia::PlatformCanvasWin* canvas) const;
 
   // |arrow_direction| determines whether the arrow is pointing to the left or
   // to the right. In RTL locales, sub-menus open from right to left and