Make View::Paint use ui::PaintRecorder to access PaintContext's canvas

ui/aura/window.h

Index: ui/aura/window.h
diff --git a/ui/aura/window.h b/ui/aura/window.h
index d6d6f7a574a84c4d4be8c62f1174932091ae259b..6c83db4b0ace870673dc813d6015b3e7a0c97ca9 100644
--- a/ui/aura/window.h
+++ b/ui/aura/window.h
@@ -369,10 +369,10 @@ class AURA_EXPORT Window : public ui::LayerDelegate,
 
   // Asks the delegate to paint the window and invokes PaintLayerlessChildren()
   // to paint any children with no layers.
-  void Paint(gfx::Canvas* canvas);
+  void Paint(const ui::PaintContext& context);
 
   // Paints any layerless children to |canvas|.
-  void PaintLayerlessChildren(gfx::Canvas* canvas);
+  void PaintLayerlessChildren(const ui::PaintContext& context);
 
   // Gets a Window (either this one or a subwindow) containing |local_point|.
   // If |return_tightest| is true, returns the tightest-containing (i.e.
@@ -464,7 +464,7 @@ class AURA_EXPORT Window : public ui::LayerDelegate,
   void OnWindowBoundsChanged(const gfx::Rect& old_bounds);
 
   // Overridden from ui::LayerDelegate:
-  void OnPaintLayer(gfx::Canvas* canvas) override;
+  void OnPaintLayer(const ui::PaintContext& context) override;
   void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip) override;
   base::Closure PrepareForLayerBoundsChange() override;