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

skia/ext/platform_canvas_mac.h

Index: skia/ext/platform_canvas_mac.h
===================================================================
--- skia/ext/platform_canvas_mac.h	(revision 6968)
+++ skia/ext/platform_canvas_mac.h	(working copy)
@@ -9,7 +9,7 @@
 
 #include "SkCanvas.h"
 
-namespace gfx {
+namespace skia {
 
 // This class is a specialization of the regular SkCanvas that is designed to
 // work with a gfx::PlatformDevice to manage platform-specific drawing. It
@@ -82,7 +82,7 @@
   PlatformCanvasMac& operator=(const PlatformCanvasMac&);
 };
 
-}  // namespace gfx
+}  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_CANVAS_MAC_H_