Change namespace from ui to gfx for NativePixmap related code

ui/gfx/native_pixmap.h

Index: ui/gfx/native_pixmap.h
diff --git a/ui/gfx/native_pixmap.h b/ui/gfx/native_pixmap.h
index 56ede7cfe803196d9f987b6a3de5136f2c35e8f3..33def81e968ddd678c6c6c8df2452d59e13d24b4 100644
--- a/ui/gfx/native_pixmap.h
+++ b/ui/gfx/native_pixmap.h
@@ -17,9 +17,6 @@
 namespace gfx {
 class Rect;
 class RectF;
-}
-
-namespace ui {
 
 // This represents a buffer that can be directly imported via GL for
 // rendering, or exported via dma-buf fds.
@@ -77,6 +74,6 @@ class NativePixmap : public base::RefCountedThreadSafe<NativePixmap> {
   DISALLOW_COPY_AND_ASSIGN(NativePixmap);
 };
 
-}  // namespace ui
+}  // namespace gfx
 
 #endif  // UI_GFX_NATIVE_PIXMAP_H_