Move DIP translation from ui/aura to ui/compositor

ash/wm/image_grid.h

Index: ash/wm/image_grid.h
diff --git a/ash/wm/image_grid.h b/ash/wm/image_grid.h
index 7b53f88ecaa3437bc716adbf32dbe4830f9b98dc..37fc37cfcc7184cc1bf0c343cd2d18d76a1a0405 100644
--- a/ash/wm/image_grid.h
+++ b/ash/wm/image_grid.h
@@ -15,10 +15,6 @@
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 
-namespace aura {
-class Window;
-}  // namespace aura
-
 namespace gfx {
 class Image;
 }  // namespace gfx
@@ -91,7 +87,7 @@ class ASH_EXPORT ImageGrid {
     DISALLOW_COPY_AND_ASSIGN(TestAPI);
   };
 
-  explicit ImageGrid(aura::Window* window);
+  ImageGrid();
   ~ImageGrid();
 
   ui::Layer* layer() { return layer_.get(); }
@@ -167,11 +163,6 @@ class ASH_EXPORT ImageGrid {
                 scoped_ptr<ui::Layer>* layer_ptr,
                 scoped_ptr<ImagePainter>* painter_ptr);
 
-  // A possibly-arbitrary window that is drawn at the same DPI
-  // (i.e. on the same monitor) as this grid.
-  // TODO(oshima): move scale factor to ui/compositor/ and remove this.
-  aura::Window* window_;
-
   // Layer that contains all of the image layers.
   scoped_ptr<ui::Layer> layer_;