Pass a ui::PaintContext from ui::Layer to layer delegates.

ui/wm/core/image_grid.cc

Index: ui/wm/core/image_grid.cc
diff --git a/ui/wm/core/image_grid.cc b/ui/wm/core/image_grid.cc
index 3f90efed7f89830ee7f07c95d7eab6f535016e74..f45e8b30f8b128b857b8b4f7090bfc21f5fb1c91 100644
--- a/ui/wm/core/image_grid.cc
+++ b/ui/wm/core/image_grid.cc
@@ -9,6 +9,7 @@
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/compositor/dip_util.h"
+#include "ui/compositor/paint_context.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_conversions.h"
@@ -266,10 +267,10 @@ void ImageGrid::ImagePainter::SetClipRect(const gfx::Rect& clip_rect,
   }
 }
 
-void ImageGrid::ImagePainter::OnPaintLayer(gfx::Canvas* canvas) {
+void ImageGrid::ImagePainter::OnPaintLayer(const ui::PaintContext& context) {
   if (!clip_rect_.IsEmpty())
-    canvas->ClipRect(clip_rect_);
-  canvas->DrawImageInt(image_, 0, 0);
+    context.canvas()->ClipRect(clip_rect_);
+  context.canvas()->DrawImageInt(image_, 0, 0);
 }
 
 void ImageGrid::ImagePainter::OnDelegatedFrameDamage(